The past 10 years have witnessed a virtual decimation of the low-income housing supply in most large American cities. During the same period, the poverty population of the cities has increased. Less low-income housing for more low-income people predestines an increase in the numbers without housing. An inadequate low-income housing supply is probably not the proximate cause of homelessness in most cases, but it is the ultimate cause of homelessness in all cases. The annual housing surveys provide a wealth of detail on a city's housing stock, both rental and owner-occupied units. There are many factors that have been discussed in connection with the revitalization of downtown and its impact on the low-income housing supply, of which three seem particularly important. These include arson, whose effect on the low-income housing supply is only dimly appreciated, abandonment and "disinvestment", and gentrification.