Understanding the Data Sources Behind U.S. Demographic Estimates: The American Community Survey (ACS) and Current Population Survey - Annual Social and Economic Supplement (CPS-ASEC)
Accurate demographic data is the cornerstone of informed policy-making, resource allocation, and a clear understanding of the evolving American population. The U.S. Census Bureau relies on several key surveys to generate these vital statistics, with the American community Survey (ACS) and the Current Population Survey – Annual Social and Economic Supplement (CPS-ASEC) playing particularly crucial roles, especially when estimating characteristics of specific populations like the foreign-born and, by extension, the residual population. This article provides a detailed overview of these two surveys, their methodologies, and why the ACS is increasingly favored for generating precise and reliable estimates.The American Community Survey (ACS): A Continuous Snapshot of American Life
The ACS is an ongoing survey, initiated in 2005, designed to provide a yearly, up-to-date portrait of the U.S. population. Unlike the decennial census, which is a complete count conducted every ten years, the ACS employs a continuous collection design, interviewing approximately 300,000 households each month. This continuous approach allows for more frequent data releases and provides a more current understanding of demographic shifts.
since 2012, the ACS has begun with an initial sample of over 3.5 million addresses annually. Addresses initially deemed non-responsive are further subsampled for follow-up interviews, resulting in a final sample size of nearly 2 million addresses since 2021, and exceeding 2.3 million in the 2010s. This robust sampling frame ensures broad representation across the nation.The ACS covers the entire U.S. population, gathering detailed information on a wide range of topics, including place of birth, year of immigration, and citizenship status – all critical data points for estimating the characteristics of the foreign-born population. Data is released annually in september and October, providing timely insights into the previous year’s demographics.For research and analysis, including the generation of residual estimates, researchers often utilize public-use samples of individual survey records. These samples represent a 1% subset of the entire U.S.population, containing over 3 million records each year as 2008 – reaching 3.4 million in 2023. A highly respected source for accessing this data is IPUMS-USA (https://usa.ipums.org/usa/), which provides user-friendly access and documentation.
The Current Population Survey – Annual Social and Economic Supplement (CPS-ASEC): A Long-Standing Tradition
The CPS-ASEC, a supplement to the monthly Current Population Survey (CPS), has a long history of providing valuable data on the U.S. population. Conducted jointly by the U.S.Bureau of Labor Statistics and the Census Bureau, the CPS currently surveys approximately 60,000 U.S. households each month.The March CPS Supplement significantly expands the questionnaire, delving into detailed information on income, government program participation, and health insurance coverage.Crucially, it also collects data on country of birth, immigration date, and citizenship - information that made it a primary source for estimating the size of the unauthorized immigrant population before the full implementation of the ACS in 2005. The March sample is intentionally broadened to include additional households with children, Hispanic individuals, and specific racial groups, enhancing it’s representativeness.
The CPS underwent a important redesign in 1994, incorporating these key demographic questions for the first time. The CPS universe encompasses the U.S. civilian noninstitutional population. Data from the March Supplement is released in September, providing insights into the previous march’s demographics. Public-use files include all participating households.
A Comparison: Why the ACS is Now Preferred
While the CPS-ASEC remains a valuable data source, the ACS has emerged as the preferred choice for generating demographic estimates, particularly for smaller populations. This is primarily due to the substantial difference in sample size.
Here’s a direct comparison based on 2023 data:
ACS: Over 3.4 million sample cases (including more than 425,000 foreign-born cases)
CPS-ASEC: 146,000 sample cases (with approximately 21,000 foreign-born cases)
This difference in scale translates directly into
