Data Dictionary: ACS 2009 (1-Year Estimates)
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Data Source: U.S. Census Bureau
Table: B99185. Imputation Of Ambulatory Difficulty For The Civilian Noninstitutionalized Population 5 Years And Over [3]
Universe: Civilian noninstitutionalized population 5 years and over
Table Details
B99185. Imputation Of Ambulatory Difficulty For The Civilian Noninstitutionalized Population 5 Years And Over
Universe: Civilian noninstitutionalized population 5 years and over
Variable Label
B99185001
B99185002
B99185003
Relevant Documentation:
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2009 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.

Ambulatory difficulty
Ambulatory difficulty was derived from question 18b, which asked respondents if they had "serious difficulty walking or climbing stairs." Prior to 2008, the ACS asked if respondents had "a condition that substantially limits one or more basic physical activities such as walking, climbing stairs, reaching, lifting, or carrying." This measure was labeled "Physical difficulty" in ACS data products.