There is a general consensus among both experts and the public at large that New York City suffers from a chronic shortage of affordable housing. For policy planning purposes it would be useful to know just how much of a shortage there is. Once the question is addressed directly, however, it quickly becomes apparent that it defies a simple answer and that underlying it are a host of value judgments about how families should live, what policies should be pursued, and how the market will respond to them.

The difficulties associated with defining housing need and anticipating market adjustments are compounded by the paucity of reliable data on marginally housed families. Standard data sources are fairly reliable when detailing characteristics of stable working families but falter when information on marginal populations is considered. The more precarious a family’s housing circumstances, the more likely they will be missed by standard data sources.