American Housing Survey
The American Housing Survey (AHS) is conducted by the US Census Bureau with releases about every two years.
National data are collected every other year, from a fixed sample of about 50,000 homes, plus new construction each year. The survey started in 1973, and has had the same sample since 1985. 47 metropolitan areas have additional samples every 4-6 years (4 years for six of the largest metro areas - Chicago, Detroit, Los Angeles, New York, Northern New Jersey, and Philadelphia - which are included with the national sample.). Since 1984, each metropolitan area is represented by a sample of at least 3,200 designated housing units. The units are divided between the central city and the rest of the metropolitan area.
The geographic units of observation are MSA's and MSA disambiguated by central cities and suburbs. The Metropolitan surveys also reference a "Zone" geography, a unique definition of the AHS that encompasses about 100,000 people. Zones have been defined by different people over the years without standard guidelines; as such they cannot easily be linked to Census geographies.