Data Dictionary: ACS 2008 (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: Universe: Civilian noninstitutionalized population
Table Details
B99183. Imputation Of Vision Difficulty For The Civilian Noninstitutionalized Population
Universe: Universe: Civilian noninstitutionalized population
Variable Label
B99183001
B99183002
B99183003
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.
 
Hearing and Vision Limitations
The data on hearing and vision limitations were derived from answers to Questions 16a and 16b. Question 16a asked respondents if they were "deaf or ... [had] serious difficulty hearing." Question 16b asked if respondents were "blind or ... [had] serious difficulty seeing even when wearing glasses." Respondents were instructed to mark "yes" or "no" for each question. Question 16a is labeled as "Hearing difficulty" and Question 16b as "Vision difficulty" for some of the disability data products such as the ACS Detailed Tables.
Limitation of the Data
The Census Bureau does not recommend trend analysis using the 2008 data with years prior to 2008 due to the questionnaire change.
Question/Concept History
The 2008 American Community Survey marks a break in the series of disability data. In the 1999 - 2007 American Community Surveys, hearing and vision limitations were captured with one question, referred in data products as "Sensory disability." As such, parsing out which limitation respondents identified with was impossible. In addition, research has showed that combining the two new measures to replicate a similar measure as the old one proved not comparable. For additional information on the differences between the 2008 ACS disability questions and prior ACS disability questions, see "2006 ACS Content Test Evaluation Report Covering Disability" (http://www.census.gov/acs/www/AdvMeth/content_test/P4_Disability.pdf).