|Data Source:||U.S. Census Bureau|
Universe: Occupied housing units
|Summary File 3 Technical Documentation -> Appendix C. Data Collection and Processing Procedures -> Glossary -> Imputation|
When information is missing or inconsistent, the Census Bureau uses a method called imputation to assign values. Imputation relies on the statistical principle of "homogeneity," or the tendency of households within a small geographic area to be similar in most characteristics. For example, the value of "rented" is likely to be imputed for a housing unit not reporting on owner/renter status in a neighborhood with multiunits or apartments where other respondents reported "rented" on the census questionnaire. In past censuses, when the occupancy status or the number of residents was not known for a housing unit, this information was imputed.
Internet Questionnaire Assistance (IQA)
An operation which allows respondents to use the Census Bureau's Internet site to (1) ask questions and receive answers about the census form, job opportunities, or the purpose of the census and (2) provide responses to the short form.
Interpolation frequently is used in calculating medians or quartiles based on interval data and in approximating standard errors from tables. Linear interpolation is used to estimate values of a function between two known values. Pareto interpolation is an alternative to linear interpolation. In Pareto interpolation, the median is derived by interpolating between the logarithms of the upper and lower income limits of the median category. It is used by the Census Bureau in calculating median income within intervals wider than $2,500.
|Summary File 3 Technical Documentation -> Appendix B. Definitons of Subject Characteristics -> Housing Characteristics -> Vehicles Available|
The data on vehicles available were obtained from answers to long-form questionnaire Item 43, which was asked on a sample basis at occupied housing units. These data show the number of passenger cars, vans, and pickup or panel trucks of 1-ton capacity or less kept at home and available for the use of household members. Vehicles rented or leased for 1 month or more, company vehicles, and police and government vehicles are included if kept at home and used for nonbusiness purposes. Dismantled or immobile vehicles are excluded. Vehicles kept at home but used only for business purposes also are excluded.
Aggregate vehicles available
To calculate aggregate vehicles available, a value of "7" is assigned to vehicles available for occupied units falling within the terminal category, "6 or more." (For more information on aggregates, see "Derived Measures".)
Vehicles per household (Mean vehicles available)
Vehicles per household is computed by dividing aggregate vehicles available by the number of occupied housing units. Vehicles per household is rounded to the nearest tenth. (For more information on means, see Derived Measures.)
Limitation of the data
The statistics do not measure the number of vehicles privately owned or the number of households owning vehicles.
Data on automobiles available were collected from 1960 to 1980. In 1980, a separate question also was asked on the number of trucks and vans. The data on automobiles and trucks and vans were presented separately and also as a combined vehicles-available tabulation. The 1990 and Census 2000 data are comparable to the 1980 vehicles-available tabulations. In 1990, the terminal category identified "7 or more"; this was changed to "6 or more" in Census 2000.