The approval given by a local jurisdiction to proceed on a construction project. Note that not all areas of the country require a permit for construction.

For estimates of housing units authorized from the Building Permits Survey, the "Universe" is defined as all unique permit offices at the time the last sample was selected. "Unique" permit offices are those jurisdictions that would not result in double reporting. For example, if a city issues zoning permits and its county issues building permits (including permits for buildings in the city(, only the county office is included in the universe. The numbers associated with the various universes (e.g., 20,000-place universe( are rounded for ease of identification:

1959 Universe included approximately 10,000 permit-issuing places and was used from January 1959 to December 1962

1963 Universe included approximately 12,000 permit-issuing places and was used from January 1963 to December 1966

1967 Universe included approximately 13,000 permit-issuing places and was used from January 1967 to December 1971

1972 Universe included approximately 14,000 permit-issuing places and was used from January 1972 to December 1977

1978 Universe included approximately 16,000 permit-issuing places and was used from January 1978 to December 1983

1984 Universe included approximately 17,000 permit-issuing places and was used from January 1984 to December 1993

1994 Universe included approximately 19,000 permit-issuing places and was used from January 1994 to December 2003

2004 Universe included approximately 19,300 permit-issuing places and was used from January 2004 to December 2014

2014 Universe includes approximately 20,100 permit-issuing places and is used from January 2014 forward

Structures not owned by any federal, state, or local government. Units in structures built by private developers with partial public subsidies or which are for sale upon completion to local public housing authorities under the HUD "Turnkey" program are all classified as private housing.

A housing unit, as defined for purposes of these data, is a house, an apartment, a group of rooms, or a single room intended for occupancy as separate living quarters. Separate living quarters are those in which the occupants live separately from any other individuals in the building and which have a direct access from the outside of the building or through a common hall.

In accordance with this definition, each apartment unit in an apartment building is counted as one housing unit. Housing units, as distinguished from "HUD-code" manufactured (mobile) homes, include conventional "site-built" units, prefabricated, panelized, sectional, and modular units.

Housing unit statistics also exclude group quarters (such as dormitories and rooming houses), transient accommodations (such as transient hotels, motels, and tourist courts), moved or relocated buildings, and housing units created in an existing residential or nonresidential structure.

Units in assisted living facilities are considered to be housing units, however, units in nursing homes are not considered to be housing units.

The valuation is the estimated value of the residential structure as shown on the building permit. If no value is listed on the permit, we accept estimates from the permit official.

When a report is not received from a building permit office, missing housing unit data are either obtained by using permits listed for the Census Bureau's Survey of Construction (SOC) or are imputed. Data from the SOC are available for only about 900 permit offices. For places not in the SOC, imputations are used. Imputations are based on the assumption that the ratio of current month or year authorizations to the prior annual total should be the same for reporting and nonreporting places.

Data labeled as "Estimates with Imputation" include the imputed data as well as reported data from the respondent or from the SOC.