This is one of the primary reasons Philadelphia has to contend with 40,000 vacant properties: the RDA and PHA are often the source of the problem.  Until a comprehensive plan is put into place, these agencies, as well as private owners and their missing heirs will continue to contribute to the blight that pervades Philadelphia’s neighborhoods.

via City Howl Help Desk: Who owns that decrepit block? The Philadelphia Redevelopment Authority | Philadelphia Daily News | 01/26/2011.