|Data Dictionary:||ACS 2008 (3-Year Estimates)|
|Data Source:||U.S. Census Bureau|
Universe: Universe: Population 16 years and over
|ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Quality Measures -> 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.
|ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Population Variables -> Work Experience -> Work Status in the Past 12 Months|
The data on work status in the past 12 months were derived from answers to Question 37. People 16 years old and over who worked 1 or more weeks according to the criteria described below are classified as "Worked in the past 12 months." All other people 16 years old and over are classified as "Did not work in the past 12 months."
|ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Population Variables -> Age|
The data on age were derived from answers to Question 4. The age classification is based on the age of the person in complete years at the time of interview. Both age and date of birth are used in combination to calculate the most accurate age at the time of the interview. Inconsistently reported and missing values are assigned or imputed based on the values of other variables for that person, from other people in the household, or from people in other households ("hot deck" imputation). Data on age are used to determine the applicability of other questions for a particular individual and to classify other characteristics in tabulations. Age data are needed to interpret most social and economic characteristics used to plan and analyze programs and policies. Therefore, age data are tabulated by many different age groupings, such as 5-year age groups.
Age Dependency Ratio
Old-Age Dependency Ratio
Child Dependency Ratio
Limitation of the Data
Caution should be taken when comparing population in age groups across time. The entire population continually ages into older age groups over time and babies fill in the youngest age group. Therefore, the population of a certain age is made up of a completely different group of people in 2000 and 2008. Since populations occasionally experience booms/increases and busts/decreases in births, deaths, or migration (for example, the postwar Baby Boom from 1946-1964), one should not necessarily expect that the population in an age group in Census 2000 should be similar in size or proportion to the population in the same age group in the 2008 ACS. For example, Baby Boomers were age 36 to 54 in Census 2000 while they were age 44 to 62 in the 2008 ACS. Therefore, the age group 55 to 59 would show a considerable increase in population when comparing Census 2000 data with the 2008 ACS data. Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations have age distributions that are very different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the age distribution. This is particularly true for areas with a substantial GQ population.
The 1996-2002 American Community Survey question asked for month, day, and year of birth before age. Since 2003, the American Community Survey question asked for age, followed by month, day, and year of birth. In 2008, an additional instruction was provided with the age and date of birth question on the American Community Survey questionnaire to report babies as age 0 when the child was less than 1 year old. The addition of this instruction occurred after 2005 National Census Test results indicated increased accuracy of age reporting for babies less than one year old.