and 8,400 Central American) and 348,000 respondents were foreign-born (92,900 Mexican and 22,200 Central American). Each year’s ACS is weighted to the current population estimates for that year with a weighting methodology that controls for small areas, race/Hispanic origin, age, gender, and marital status/households (see U.S. Census Bureau, 2009, for details). The annual ACS aggregates the 12 monthly samples to yield annual data. The U.S. Census Bureau does not release information about the dates interviews were conducted and, therefore, there is no specific “reference date” within the year for the survey.1 Immigration-related questions asked by the ACS include nativity/citizenship (but not legal status), year of arrival in the United States,2 country of birth, year of naturalization, residence 12 months before interview, and language spoken at home.

The U.S. Department of Homeland Security (DHS) uses the ACS to estimate the size of the unauthorized immigrant population residing in the United States (see Box 3-1). DHS has published annual estimates for 2006-2011 using the ACS data for 2005-2010 (Hoefer et al., 2011).

CURRENT POPULATION SURVEY

The CPS is the primary source of labor force statistics for the U.S. population and is also the source of high-profile economic statistics such as the national unemployment rate. The CPS, which is sponsored by the U.S. Census Bureau and the U.S. Bureau of Labor Statistics, is administered monthly by the U.S. Census Bureau (Grieco and Rytina, 2011). This survey frequently includes specialized supplements, and the Annual Social and Economic Supplement (ASEC), conducted in February-April each year, has an expanded sample (a double sample of Hispanic households and an oversample of other minority households and households with children). Although monthly data are generally limited to labor force items and education, a broad range of social, economic, and demographic data are collected in the CPS ASEC (formerly known as the “March supplement”).

The target population of the CPS is the civilian non-institutional population living in the United States. The sampling frame is a list of housing addresses obtained from the most recent decennial census and updated with new housing units built after the census. The CPS ASEC also includes military personnel living in off-base housing with civilian adult household members. In 2011, the average monthly sample (from January to November) in the public-use sample included 54,000 households and

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1 The ACS is weighted using population estimates for July 1 of the survey year.

2 The question about year of arrival can be subject to various interpretations for circular migrants, and estimates of migration based on year of arrival tend to be higher than those based on residence 1 year ago.



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