DEFINITIONS

A housing start is defined as the start of construction of a new housing unit, when located within a new building which is intended primarily as a house keeping residential building designed for nontransient occupancy. Start of construction for private housing units is defined as the beginning of excavation for the footings or foundation of a building; for public housing units. it is defined as when the construction contract is awarded. All housing units in a multi-family building are counted as being started when excavation for the building is started.

A housing unit is a single room or group of rooms intended for occupancy as separate living quarters by a family, by a group of unrelated persons living together, or by a person living alone. Separate living quarters are those in which the occupants do not live and eat with any other persons in the structure and which have either (1) direct access from the outside of the building or through a common hall which is used or intended to be used by the occupants of another unit or by the general public; or (2) complete kitchen facilities for the exclusive use of the occupants.

A housekeeping residential building is one consisting primarily of housing units. New housing starts exclude group quarters (such as dormitories and rooming houses), transient accommodations (such as transient hotels, motels, and tourist courts), mobile homes (trailers), moved or relocated buildings, and housing units created in an existing residential or nonresidential structure. However, in a building combining substantial residential and nonresidential floor areas, every effort is made to include the residential units in these statistics even though the primary function of the entire building is for nonresidential purposes.

Housing units, as distinguished from mobile homes, include conventional "stick built" units, prefabricated, panelized, componentized, sectional and modular units. Except for table 8, mobile homes-single wide and multi-wide-are excluded from the statistics. A mobile home is defined as a portable dwelling constructed to be towed on its own chassis and designed for use without a permanent foundation; it is manufactured with the running gear an integral part of the unit and can be towed from site to site.

Publicly owned housing includes housing units in buildings for which construction contracts were awarded by Federal, State or local governments. Units in structures built by private developers for sale upon completion to local public housing authorities under the U.S. Department of Housing and Urban Development "Turnkey" program are classified as private housing.

The statistics, by type of structure, refer to the structural characteristics of the building. The one-unit structure category includes fully detached, semidetached (semiattached, side-byside), rowhouses, and townhouses. In the case of attached units, each must be separated from the adjacent unit by an unbroken ground-to-roof party wall in order to be classified as a oneunit structure. Units built one on top of another and those built side-by-side which do not have an unbroken ground-toroof party wall and/or have common facilities, i.e., attic, basement, heating plant, plumbing, etc., are classified by the number

of units in the structure (i.e., two-unit structure, three-unit structure, etc.). In these statistics, apartment buildings are defined as buildings containing five units or more. Apartments in a conventional-type apartment building may share a common basement, heating plant, stairs, entrance halls, and water supply and sewerage disposal facilities. Townhouse apartments, though attached, are not separated by an unbroken ground-to-roof party wall and share some interstructural facilities such as water supply, sewerage disposal, etc.

Ownership is not the criterion for structural classifications in this report. A condominium apartment building is classified with apartment buildings in structures with five units or more despite the fact that each unit is individually owned. Condominium townhouses may be in the one unit category if each unit is separated from its neighbor by an unbroken ground to roof party wall (no commonly shared interstructural facilities), or in the multiunit building categories if they are not separated from each other by an unbroken ground-to-roof party wall (share interstructural facilities).

The standard census geographic regions are used in the tables of this report. States contained in each region are as follows: Northeast-Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, and Pennsylvania; North Central-Ohio, Indiana, Illinois, Michigan, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, and Kansas; South-Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Kentucky, Tennessee, Alabama, Mississippi, Arkansas, Louisiana, Oklahoma, and Texas; WestMontana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada, Washington, Oregon, California, Alaska, and Hawaii.

The distribution of housing starts between units inside and outside Standard Metropolitan Statistical Areas (SMSA's) is based on the definitions published by the Office of Management and Budget in Standard Metropolitan Statistical Areas. Data for the period beginning January 1976 are based on the 1974 definitions as amended August 1975; data for the period January 1975-December 1975 are based on the 1967 definitions, as amended April 1974; data for the period January 1974December 1974 are based on the 1967 definitions, as amended November 1973; data for April 1973-December 1973 are based on the 1967 definitions as amended February 1973; data for April 1968-March 1973 are based on 1967 defintions.

HOUSING STARTS COMPILATION

The compilation of the housing starts series is a multistage. process. First, an estimate is made monthly of the number of housing units for which building permits have been issued in all 14,000 permit-issuing places (table 6). The preliminary estimate of building permit authorizations is based on a sample of 2,800 permit-issuing places. The revised estimate is based on a sample of 6,800 of these 14,000 jurisdictions.

Second, within 137 sampled land areas (counties or groups of counties) an independent survey is conducted monthly in a subsample of the permit-issuing places (approximately 950)

to estimate the rate at which permit authorized buildings are started. In each place a sample of building permits is selected. For each permit selected, an inquiry is made of the owner or the builder to determine in which month and year the unit(s) covered by the permit was (were) started. In case the units authorized by permits in a particular month are not started by the end of that month, follow-ups are made in successive months to find out when the units were actually started.

From this sample of permits, ratios are calculated (by type of structure) of the number of units started to the number of units covered by permits; separate ratios are calculated for units started from permits of that month and of each preceding month. These ratios or start rates are then applied to the appropriate estimate of the number of units authorized by permits (preliminary based on the 2,800 place sample or final based on the 6,800 place sample) to provide estimates of the number of units started for each month of authorization. These estimates are aggregated to structural totals within the four Census regions.

Having produced estimates of the number of units started with permit authorization, two additional adjustments are made.

1. An upward adjustment of 3.3 percent is made to the number of one-unit structures (single family houses) started to take care of those units started within permit-issuing areas but without permit authorization. (A study spanning a four year period indicated that permits were obtained for all buildings with two housing units or more.)

2. Upward imputations are made to account for those units started prior to permit authorization and for late reports.

The results of the procedures outlined above are the published estimates for housing units started in the 14,000 permitissuing places (table 3).

Third, an estimate of the number of units started in areas where building permit systems do not exist is made. Within the 137 sampled land areas, visits are made to a select group of persons who are presumed most likely to know about local housing activities in those areas not covered by permit jurisdictions. A list is obtained from them of all residential buildings they know to have been started within these areas during the preceding month. The information provided by these sources is verified by field visit or by telephone interview with the owner or builder. In addition, a subsample of 100 small land areas is canvassed intensively by Census employees who look for all units started since the previous month, identifying those not reported by the sources as well as those reported by them. This canvass provides a basis for estimating the number of units not reported by the local sources. Units not reported by local sources are then added to the number of units reported by these sources, with appropriate weighting, to provide an estimate of total housing starts in areas not covered by building permit systems.

Addition of this estimate of starts in nonpermit areas to the estimate of starts in the 14,000 permit-issuing places results in an estimate of total private housing units started (table 2).

Fourth, information on public housing starts is obtained, for the most part, from the agencies involved, e.g., Department of Housing and Urban Development, Department of Defense, etc. (table 4). Combining private and public starts results in an estimate of total units started (table 1).

STARTS BY TYPE OF STRUCTURE

A total of 14 different sets of starts rates that change from month to month are employed to calculate number of housing units started by type of structure in permit places. Eight sets of starts rates are used for one-family houses: separate sets of rates for metropolitan and nonmetropolitan areas within each of the four regions. For structures with five units or more, separate sets of starts rates are used for each of the four regions. Single sets of starts rates are used for all regions for structures with two units and for structures with three to four units.

Starts by type of structure in nonpermit areas are calculated directly in the estimating procedure described above.

BUILDING PERMITS

Data on housing units authorized by local building permits relate to the time of issuance rather than to the actual start of construction. They do, however, provide some indication of activity in residential building in advance of the start of actual construction. Although construction is started on most residential buildings in the same month in which the permit is issued, several months may pass before start of construction.

The 14,000 areas with local building permit systems for which figures are currently given in this report (table 6) account for a major portion of residential building in the United States. For the country as a whole, approximately 82 percent of the private housing units were constructed in permit-issuing places in 1977.

The monthly series and 1973 through 1976 annual data reflect the 14,000 places in the United States which were identified in 1972 as having local building permit systems. Annual data for both the 13,000 and 14,000 places are shown for 1971 and 1972. Annual data for 1968 through 1970 reflect the 13,000 places identified in 1967 as having local building permit systems.

Basically, the procedure followed in arriving at the monthly building permit authorization totals involves the cumulating of monthly data from all permit-issuing places that authorized 50 housing units or more (20 or more in some states) in a recent year along with estimates for the less active places based on a stratified probability sample of these places.

A more detailed discussion of the uses and limitations of building permit data is provided in the Census Bureau's monthly report on Housing Authorized by Building Permits and Public Contracts (C40).

MOBILE HOME SHIPMENTS

Beginning with the data for November 1977, the statistics on manufacturers' shipments of mobile homes produced by the National Conference of States on Building Codes and Standards (NCSBCS) are published in this report in lieu of those previously provided by the Manufactured Housing Institute