A start is defined as excavation (ground breaking) for the footings or foundation of a residential structure. For a multifamily structure, all units are counted as started when the structure is started.
Starts are estimated by the Census Bureau based on a survey of permit holders. Each month, Census Bureau representatives ask holders of outstanding permits whether they have started construction. The same survey also determines whether the home is being built for sale (as a package including land), and if so, whether it has been sold. The Census Bureau continues to contact the permit holders each month until the structure is completed (or if completed but still for-sale, until a sale occurs). For single-family homes, about one in every 50 permits is selected for the survey.
Although about half of single family homes are started in the same month that the permit is issued, and more than 90 percent are started within 2 months of the month of issuance, the Census Bureau will continue to track unused permits for 60 months. For multifamily units, more than one-third are started in the same month as authorization, and about 80 percent are started within 2 months.
The “Survey of Construction” forms are filled out by Census Bureau personnel, with most data collected by phone. Construction sites are visited only where the permit holder cannot be contacted or is uncooperative. The survey also collects other characteristics of new homes, such as the size, number of bedrooms, exterior wall material, type of heating system, lot size, estimated current lot value, and sale price.
Institutional structures and group quarters, such as dormitories, nursing homes, or transient hotels, are excluded.
For the few places where permits are not required or reported, the Census Bureau sends representatives to a random sample of land parcels, to see whether any homes are being built.
Single-family structures are distinguished based on information collected in the survey, even if the permit was characterized as multifamily by the permit-issuing jurisdiction.