Data Dictionary: Census 2010
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Survey: Census 2010
Data Source: Census Bureau; Social Explorer
Table: P20. Households By Presence Of People Under 18 Years By Household Type By Age Of People Under 18 Years [34]
Universe: Households
Table Details
Source: 2000 SF1 P19. A household that has at least one member of the household related to the householder by birth, marriage, or adoption is a "Family household." Same-sex couple households are included in the family households category if there is at least one additional person related to the householder by birth or adoption. Same-sex couple households with no relatives of the householder present are tabulated in nonfamily households. Responses of "same-sex spouse" were edited during processing to "unmarried partner." "Nonfamily households" consist of people living alone and households which do not have any members related to the householder.
Relevant Documentation:
Excerpt from: Social Explorer, U.S. Census Bureau; 2010 Census of Population and Housing, Summary File 1: Technical Documentation, Issued June 2011.
A household includes all the people who occupy a housing unit. (People not living in households are classified as living in group quarters.) A housing unit is a house, an apartment, a mobile home, a group of rooms, or a single room that is occupied (or if vacant, is intended for occupancy) as separate living quarters. Separate living quarters are those in which the occupants live separately from any other people in the building and which have direct access from the outside of the building or through a common hall. The occupants may be a single family, one person living alone, two or more families living together, or any other group of related or unrelated people who share living arrangements. In the 2010 Census data products, the count of households or householders equals the count of occupied housing units.

Average Household Size
Average household size is a measure obtained by dividing the number of people in households by the number of households. In cases where people in households are cross-classified by race or Hispanic origin, people in the household are classified by the race or Hispanic origin of the householder rather than the race or Hispanic origin of each individual. Average household size is rounded to the nearest hundredth.

Excerpt from: Social Explorer, U.S. Census Bureau; 2010 Census of Population and Housing, Summary File 1: Technical Documentation, Issued June 2011.
The data on age were derived from answers to a two-part question (i.e., age and date of birth). The age classification for a person in census tabulations is the age of the person in completed years as of April 1, 2010, the census reference date. Both age and date of birth responses are used in combination to
determine the most accurate age for the person as of the census reference date. Inconsistently reported and missing values are assigned or allocated based on the values of other variables for that person, from other people in the household or from people in other households (i.e., hot-deck imputation).
Age data are tabulated in age groupings and single years of age. Data on age also are used to classify other characteristics in census tabulations.

Median Age
This measure divides the age distribution into two equal parts: one-half of the cases falling below the median value and one-half above the value. Median age is computed on the basis of a single-year-of-age distribution using a linear interpolation method.

Limitation of the data
There is some tendency for respondents to provide their age as of the date they completed the census questionnaire or interview, not their age as of the census reference date. The two-part question and editing procedures have attempted to minimize the effect of this reporting problem on tabulations. Additionally, the current census age question displays the census reference date prominently, and interviewer training emphasizes the importance of collecting age as of the reference date.

Respondents sometimes round a persons age up if they were close to having a birthday. For most single years of age, the misstatements are largely offsetting. The problem is most pronounced at age 0. Also, there may have been more rounding up to age 1 to avoid reporting age as 0 years. (Age in completed months was not collected for infants under age 1.) Editing procedures correct this problem.

There is some respondent resistance to reporting the ages of babies in completed years (i.e., 0 years old when the baby is under 1 year old). Instead, babies ages are sometimes reported in months. The two-part question along with enhanced editing and data capture procedures correct much of this problem before the age data are finalized in tabulations. Additionally, the current census age question includes an instruction for babies ages to be answered as 0 years old when they are under 1 year old.

Age heaping is a common age misreporting error. Age heaping is the tendency for people to overreport ages (or years of birth) that end in certain digits (commonly digits 0 or 5) and underreport ages or years of birth ending in other digits. The two-part question helps minimize the effect of age heaping on the final tabulations.

Age data for centenarians have a history of data quality challenges. The counts in the 1970 and 1980 Censuses for people 100 years and over were substantially overstated. Editing and data collection methods have been enhanced in order to meet the data quality challenges for this population.

It also has been documented that the population aged 69 in the 1970 Census and the population aged 79 in the 1980 Census were overstated. The population aged 89 in 1990 and the population aged 99 in 2000 did not have an overstated count. (For more information on the design of the age question, see the Comparability section below.)

Age data have been collected in every census. However, there have been some differences in the way they have been collected and processed over time. In the 2010 Census (as in Census 2000), each individual provided both an age and an exact date of birth. The 1990 Census collected age and year of birth. Prior censuses had collected month and quarter of birth in addition to age and year of birth. The 1990 Census change was made so that coded information could be obtained for both age and year of birth.

In each census since 1940, the age of a person was assigned when it was not reported. In censuses before 1940, with the exception of 1880, people of unknown age were shown as a separate category. Since 1960, assignment of unknown age has been performed by a general procedure described as imputation. The specific procedures for imputing age have been different in each census. (For more information on imputation, see 2010 Census: Operational Overview and Accuracy of the Data.)