Urban decay

Urban decay is the process in which a city or area goes into conditions of disrepair or becomes decrepit or filled with blight. Urban decay involves white flight, population changes, depopulation, economic troubles, high local unemployment, higher than usual crime and political issues. Blight is associated with condemned properties, empty lots and deserted areas that often attract criminal activity. That includes squattiing in these buildings/homes, 
Related pages.
Rust Belt 
Deindustrialization 
Ruins 
Ghost town