Data Dictionary: ACS 2009 (1-Year Estimates)
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Data Source: U.S. Census Bureau
Table: B99183. Imputation Of Vision Difficulty For The Civilian Noninstitutionalized Population [3]
Universe: Civilian noninstitutionalized population
Table Details
B99183. Imputation Of Vision Difficulty For The Civilian Noninstitutionalized Population
Universe: Civilian noninstitutionalized population
Variable Label
B99183001
B99183002
B99183003
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.

Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2009 Summary File: Technical Documentation.
 
Vision difficulty
Vision difficulty was derived from question 17b, which asked respondents if they were "blind or ... (had) serious difficulty seeing" even when wearing glasses. Prior to the 2008 ACS, hearing and vision difficulty were asked in a single question under the label "Sensory disability."