Around three dozen US cities with populations of more than 100,000 in 1950 have lost at least 20% of their residents. Deborah and Frank Popper have argued that their Buffalo Commons concept, originally conceived as a means to revivify the depopulating Great Plains, can be adapted for use in these new urban prairies. When it was announced in 2002, Baltimore's anti-blight Project 5000 aimed to acquire 5,000 vacant and abandoned properties by aggressively pursuing tax sale foreclosures, quick-takes, and traditional acquisitions. The city asked local law firms, title companies, and related businesses to help clear titles, and by 2007 had acquired and cleared title of more than 6,000 properties. Michigan changed its tax foreclosure law in 1999 to give county governments greater authority in gaining control of abandoned property County or state tax foreclosures can be completed within two years and abandoned property can be transferred in only one.