Estimating the World Trade Center Tower Population on September 11, 2001: A Capture–Recapture Approach

RTI International, 230 W Monroe St, Suite 2100, Chicago, IL 60606, USA.
American Journal of Public Health (Impact Factor: 4.55). 12/2008; 99(1):65-7. DOI: 10.2105/AJPH.2007.124768
Source: PubMed


I applied the capture-recapture method to estimate the World Trade Center tower population at the time of the September 11, 2001, terrorist attacks. Available lists helped identify 8965 survivors and 2152 confirmed casualties. The capture-recapture model suggested that an additional 4435 survivors were present, putting the total count of all present at 15,552 (95% confidence interval=15,216, 15,897). An accurate estimate represents the potential number at risk for trauma as a result of direct exposure to the events of the day.

Full-text preview

Available from:
  • Source
    • "The goal of the analysis is to estimate the total number of individuals N in the population; this amounts to predicting the number of individuals that do not appear on any list. An early discussion of this problem appears in IWGDMF (International Working Group for Disease Monitoring and Forecasting) (1995a,b) and several applications can be found in the literature, see for instance chapter 6 of Bishop, Fienberg, and Holland (1975), Bruno, Biggeri, LaPorte, McCarty, Merletti , and Pagano (1994), Murphy (2009). A key assumption highlighted by Hook and Regal (1993) is that of constant catchability by each source. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This work considers the estimation of the size N of a closed population using incomplete lists of its members. Capture histories are constructed by establishing the presence or the absence of each individual in all the lists available. Models for data featuring a heterogeneous catchability and list dependencies are considered. A log-linear model leading to a lower bound for the population size is derived for a known set of list dependencies and a latent catchability variable with an arbitrary distribution. This generalizes Chao’s lower bound to models with interactions. The proposed model can be used to carry out a search for important list interactions. It also provides diagnostic information about the nature of the underlying heterogeneity. Indeed, it is shown that the Poisson maximum likelihood estimator of N under a dichotomous latent class model does not exist for a particular set of LB models. Several distributions for the heterogeneous catchability are considered; they allow to investigate the sensitivity of the population size estimate to the model for the heterogeneous catchability.
    Preview · Article · Jan 2011 · The International Journal of Biostatistics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To date there have been no comprehensive reports of the work performedby 9/11 World Trade Center responders. 18,969 responders enrolled in the WTC Medical Monitoring and Treatment Program were used to describe workers’ pre-9/11 occupations, WTC work activities and locations from September 11, 2001 to June 2002. The most common pre-9/11 occupation was protective services (47%); other common occupations included construction, telecommunications, transportation, and support services workers. 14% served as volunteers. Almost one-half began work on 9/11 and >80% reported working on or adjacent to the ‘‘pile’’ at Ground Zero. Initially,the most common activity was search and rescue but subsequently, the activities of most responders related to their pre-9/11 occupations. Other major activities included security; personnel support; buildings and grounds cleaning; and telecommunications repair. The spatial, temporal, occupational, and task-related taxonomy reported here will aid the development of a job-exposure matrix, assist in assessment of disease risk, and improve planning and training for responders in future urban disasters.
    Full-text · Article · Sep 2011 · American Journal of Industrial Medicine