Data Dictionary: ACS 2008 (1-Year Estimates)
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Data Source: U.S. Census Bureau
Table: B99082. Imputation Of Private Vehicle Occupancy [5]
Universe: Workers 16 years and over
Table Details
B99082. Imputation Of Private Vehicle Occupancy
Universe: Workers 16 years and over
Variable Label
B99082001
B99082002
B99082003
B99082004
B99082005
Relevant Documentation:
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2008 Summary File: Technical Documentation.
 
Imputation Rates
Missing data for a particular question or item is called item nonresponse. It occurs when a respondent fails to provide an answer to a required item. The ACS also considers invalid answers as item nonresponse. The Census Bureau uses imputation methods that either use rules to determine acceptable answers or use answers from similar housing units or people who provided the item information. One type of imputation, allocation, involves using statistical procedures, such as within-household or nearest neighbor matrices populated by donors, to impute for missing values.
Overall Person Characteristic Imputation Rate
This rate is calculated by adding together the weighted number of allocated items across a set of person characteristics, and dividing by the total weighted number of responses across the same set of characteristics.
Overall Housing Characteristic Imputation Rate
This rate is calculated by adding together the weighted number of allocated items across a set of household and housing unit characteristics, and dividing by the total weighted number of responses across the same set of characteristics. These rates give an overall picture of the rate of item nonresponse for a geographic area.

Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2008 Summary File: Technical Documentation.
 
Private Vehicle Occupancy
The data on private vehicle occupancy were derived from answers to Question 31. This question was asked of people who indicated in Question28 that they worked at some time during the reference week and who reported in Question 30 that their means of transportation to work was "Car, truck, or van." Data were tabulated for workers 16 years old and over, that is, members of the Armed Forces and civilians who were at work during the reference week. (See "Reference Week".)

Private vehicle occupancy refers to the number of people who usually rode to work in the vehicle during the reference week. The category, "Drove alone," includes people who usually drove alone to work as well as people who were driven to work by someone who then drove back home or to a non-work destination. The category, "Carpooled," includes workers who reported that two or more people usually rode to work in the vehicle during the reference week.
Limitation of the Data
Beginning in 2006, the Group Quarters (GQ) population is included in the ACS. Some types of GQ populations may have private vehicle occupancy distributions that are different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the private vehicle occupancy distribution. This is particularly true for areas with a substantial GQ population.
Question/Concept History
Beginning in 1999, the American Community Survey questions differ from the 1996-1998 questions only in the format of the skip instructions.