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Data Dictionary: ACS 2008 (3-Year Estimates)
you are here: choose a survey survey data set table variable details
Data Source: U.S. Census Bureau
Universe: Universe: Nonfamily households
Relevant Documentation:
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.
  ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Derived Measures -> Aggregate
Aggregate
An aggregate is the sum of the values for each of the elements in the universe. For example, aggregate household income is the sum of the incomes of all households in a given geographic area. Means are derived by dividing the aggregate by the appropriate universe. When an aggregate used as a numerator is rounded in the detailed (base) tables, the rounded value is used for the calculation of the mean.
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.
  ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Population Variables -> Income in the Past 12 Months -> Income of Households
Income of Households
This includes the income of the householder and all other individuals 15 years old and over in the household, whether they are related to the householder or not. Because many households consist of only one person, average household income is usually less than average family income. Although the household income statistics cover the past 12 months, the characteristics of individuals and the composition of households refer to the time of interview. Thus, the income of the household does not include amounts received by individuals who were members of the household during all or part of the past 12 months if these individuals no longer resided in the household at the time of interview. Similarly, income amounts reported by individuals who did not reside in the household during the past 12 months but who were members of the household at the time of interview are included. However, the composition of most households was the same during the past 12 months as at the time of interview.
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.
  ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Population Variables -> Income in the Past 12 Months -> Adjusting Income for Inflation
Adjusting Income for Inflation
Income components were reported for the 12 months preceding the interview month. Monthly Consumer Price Indices (CPI) factors were used to inflation-adjust these components to a reference calendar year (January through December). For example, a household interviewed in March 2008 reports their income for March 2007 through February 2008. Their income is adjusted to the 2008 reference calendar year by multiplying their reported income by 2008 average annual CPI (January-December 2008) and then dividing by the average CPI for March 2007-February 2008.

In order to inflate income amounts from previous years, the dollar values on individual records are inflated to the latest years dollar values by multiplying by a factor equal to the average annual CPI-U-RS factor for the current year, divided by the average annual CPI-U-RS factor for the earlier/earliest year.
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.
  ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Population Variables -> Sex
Sex
The data on sex were derived from answers to Question 3. Individuals were asked to mark either "male" or "female" to indicate their sex. For most cases in which sex was not reported, the appropriate entry was determined from the persons given (i.e., first) name and household relationship. Otherwise, sex was imputed according to the relationship to the householder and the age of the person.
Sex Ratio
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The sex ratio represents the balance between the male and female populations. Ratios above 100 indicate a larger male population, and ratios below 100 indicate a larger female population. This measure is derived by dividing the total number of males by the total number of females and then multiplying by 100. It is rounded to the nearest tenth.
Limitation of the data
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Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations have sex distributions that are very different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the sex distribution. This is particularly true for areas with a substantial GQ population.

The Census Bureau tested the changes introduced to the 2008 version of the sex question in the 2007 ACS Grid-Sequential Test (http://www.census.gov/acs/www/Downloads/ACS-MP-09_Grid-Sequential_Test_Final_Report.pdf).

The results of this testing show that the changes may introduce an inconsistency in the data produced for this question as observed from the years 2007 to 2008
Question/Concept History
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Beginning in 2008, the layout of the sex question response categories was changed to a horizontal side-by-side layout from a vertically stacked layout on the mail paper ACS questionnaire.
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.
  ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Population Variables -> Household Type and Relationship -> Relationship to Householder -> Householder
Householder
The data on relationship to householder were derived from answers to Question 2, which was asked of all people in housing units. One person in each household is designated as the householder. In most cases, this is the person, or one of the people, in whose name the home is owned, being bought, or rented and who is listed on line one of the survey questionnaire. If there is no such person in the household, any adult household member 15 years old and over could be designated as the householder. Households are classified by type according to the sex of the householder and the presence of relatives. Two types of householders are distinguished: a family householder and a non-family householder. A family householder is a householder living with one or more individuals related to him or her by birth, marriage, or adoption. The householder and all people in the household related to him or her are family members. A non-family householder is a householder living alone or with non-relatives only.
Excerpt from: Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.
  ACS 2008-3yr Summary File: Technical Documentation -> Appendix B: Subject Definitions -> Population Variables -> Age
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.
Median Age
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The median age is the age that divides the population into two equal-size groups. Half of the population is older than the median age and half is younger. Median age is based on a standard distribution of the population by single years of age and is shown to the nearest tenth of a year. (See the sections on "Standard Distributions" and "Medians" under "Derived Measures.")
Age Dependency Ratio
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The age dependency ratio is derived by dividing the combined under-18 and 65-and-over populations by the 18-to-64 population and multiplying by 100.
Old-Age Dependency Ratio
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The old-age dependency ratio is derived by dividing the population 65 years and over by the 18-to-64 population and multiplying by 100.
Child Dependency Ratio
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The child dependency ratio is derived by dividing the population under 18 years by the 18-to-64 population, and multiplying by 100.
Limitation of the Data
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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.
Question/Concept History
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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.