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   
 
  
  

           
          
           
             
           
          
           
          
            
             
           
          
        
      

       
              
              
           
            
            
         
    
            
              

             
           
           
           
              
             
             
             
           
              
          
             
           
            
            
          
          
   
              
           
            
            
            
               
             
            
             
              
           
            
          
            
          
            
                
              
            
 
              
            
            
            
         
              
             
      
            
              
           
               
             
             
          
             
              
   
            
              
           
         
          
             
            
             
             
                 
          
               
             
          
              
          
         
          
            
              
           
            
         
           
                 
             
   
          
           
             
            
     
           
             
               
            
             
             
             
              
             
          
          
           
           
          
           
             
            
           
             
           
           
          
             
            
           
             
           
              
            
             
      
        
              
          
            
              
             
              
           
    
             
            
            
               
            
             
             
               
             
               
           
            
           
          
   
             
                
            
           
           
            
            
              
         
            
        
                 
      
             
           
            
               
       
          
              
          
              
          
              
          
               
            
             
            
              
             
             
               
             
             
         
        
          
             
               
          
           
            
               
                 
     
             
             
             
              
        
             
          
              
           
             
               
            
              
          
               
             
     
         
 
         
              
                 
            
              
   
              
             
            
              
             
              
              
           
            
           
          
           
      
    
            
             
            
           
           
           
            
                
   
             
    
         
            
           
             
              
           
           
             
             
          
             
           
           
        
           
           
               
          
           
             
              
           
             
            
  0.5·Σ|sipi|  si     pi     
            

               
          
            
          
              
           
           
           
            
           
               
             
              
              
           
            
             
         
             
        
  
             
           
              


               
         
               
     
              
              
                
              
            
           
              
              

            
              
         
           
                  
              
             
              
            
                
                
 
               
                  
                
                   
          
             

              
             
              
              
              
            
           
           
     
  
    ∗∗∗ ∗∗∗
 
    

    

    

   ! ! !
   ! ! !
   
      
     
            
      
             
            
          
               
             
                
            
     

                
            
            
               
           
           
             
            
          
             
              
 
            
          
             
              
              
           
          
            
  
               
         
               
                
           

    
              
 i  tit        it
          it   
  Xkit        T1tT2t  
  α1iα2i             
         "1it "2it    
               
               
           
it =πit +Σβ1kXkit +T1t+α1i+"1it 
it =τ
!
it +Σβ2kXkit +T2t+α2i+"2it 
             
            
           
               
             
         
            
              
            
           
             
            

    
            
      
 
   
 
  !
   ! !
  
     
      
     
    
            
            

              
            
           
           
             
           
              
             
             
          
   
             
              
             
   

              
              
 
 
            
                 
             
             
             
            
          
             
                
              
    
             
             
             
               
 "        "    
            
        "      
     
           H0:τ=0 E( ·"2it )=0
               
  "  $1 = "110

  2,353 ×0.249           
          "   
               
            
             
            
              
        
     
 
   
         
   
  ! !
   ! ! ! !
     
       
      
             α%
            
             
               
 
 
              
               
            
              
            

          
            
        
               
              
            
             
             
   

   



  

   




              
            
             
    
           
               
             
                 
                 
           
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            
              
            
             
             
           
           
               
            
              
               
      τ=.061,s.e.
τ=.090
              
               
               
          
             
            
           
              
                 
      
              
               
               
                
               
             
                 
                
             
                  
   

              
               
             
     
   
 


 
 



   
  
        
  
   ! ! !
      
       
       
       
      
     
           
           α%    
            
            
                  
        ×     
            

            
          
              
            

              
            
            
           
             
             
               
            
            
              
          
            
             
          
             t+1
        t         
   t                
 
               
                
              
                
                 

                 
              
             
                

             
             
                
           
                
             
         
           
             
           
            
             
              
           
            
             
               
            
              
            

            
           
              
           
               

               
              
          
             
            
            
              
      
   
           
               
               
            
              
             
          
           
            
        
            
            
                 
            
           
            

              
                
 
              
           
             
              
               
           "  
         =4.31 ×0.00067 
              
        "   
              
              
              
            
               
            
            
            
                
                
                    
                
             
                 
         
               
             
                  
    

           
              
        
        
     
   
         
   
   ! ! ! !
       
        
       
       
      
        
     
   
         
   
   ! ! ! !
       
        
       
       
      
           
           α%    
            
            
               
          

          
               
             
              
  
          
             
            
           
              
              
            
         
           
                
                 
               
            
           
       
             
         
             
            
            
                
                  

            
            
        
           
            
               
                
            
             
            
              
              
  
             
               
              
           
            
            
              
               
             
     


            
            
            
            
            
             
           
           
                  
          
              
            
             
            
         
          
            
           
          
              
       
           
           
               

          
            
              
            
              
             
               
          
           
             
             
             
           

        
   
          
    
             
          
 
             
        

         
    

           
        
   
             
    
          
  
           
      
             
      
         
           
   
          
     
          
   
             
       
         
 
            
           

           
         
        
          
       
             
   

           
          
 
             
         

          
     
           
  
         
        
          
        

              
       
 
          
    
           
     
              
          
 
           
  
            
         
   
           
   
          
        
 

         
      
        
     
           
 
           
     
          
        
   
         
         

           
          
   
         

            
      
          
     
  
            
  
          
        
          

           
        
          

              
      
          
     
           
         
  
          
  
           
          
   
          
            
   
              
         
 
            
      
          
        

           
   
           
     
  
             
  
 
           


           
       
            
      
            
   
 
      
           
        

           
        
             

         
        
  
          
      
          
       

          
     
          
          
    
         
     
            
         
 

          
          

             
     
         
    
 
 
           
           
  
            
   
             
          
           
   
            
          

          
  
            
    
           
           
    
             
 
          
   
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