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How the Census Bureau Measures Income and Poverty

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The U.S. Census Bureau releases income, poverty and health insurance statistics from its Current Population Survey Annual Social and Economic Supplement, known as CPS ASEC, every September. It also releases one-year statistics from the 2019 American Community Survey (ACS) later this month. 

The national statistics from these surveys are not identical because they collect income data differently.

The CPS is the Census Bureau’s longest-running survey. Conducted monthly, it serves as the nation’s primary source of statistics on labor force characteristics. Supplemental surveys are added in most months. The CPS ASEC provides statistics on income, poverty, age, sex, race, marital status, educational attainment, employee benefits, work schedules, school enrollment, health insurance, noncash benefits and migration. We primarily collect data for this supplement in March of each year.

The CPS ASEC asks detailed questions categorizing income into over 50 sources. The key purpose of the CPS ASEC is to provide timely and detailed estimates of income and poverty and to measure change in these national-level estimates. The CPS ASEC is the official source of the national poverty estimates calculated in accordance with the Office of Management and Budget’s Statistical Policy Directive 14. For more information on the CPS ASEC, visit <www.census.gov/programs-surveys/cps.html>.

The American Community Survey (ACS), on the other hand, is the only source of small-area statistics available on a wide range of important social and economic characteristics for all communities in the country. In addition to income, poverty and health insurance, other topics include education, language ability, the foreign-born population, marital status, migration, homeownership, the cost and value of homes, and many more.

The ACS has an annual sample size of about 3.5 million addresses in the United States and Puerto Rico, and includes both housing units and group quarters (e.g., nursing homes and prisons). We conduct this survey in every county in the nation and every municipality or municipio in Puerto Rico (where it is called the Puerto Rico Community Survey). Beginning in 2006 (2005 data year), the survey data have been released annually for geographic areas with populations of 65,000 and greater. For information on the ACS sample design and other topics, visit <www.census.gov/programs-surveys/acs>.

Statistics from these two surveys may differ for multiple reasons. First, income questions in the CPS ASEC are much more detailed than the summary questions asked in the ACS. Second, interviewers administer the CPS ASEC survey in person or over the phone, while people primarily respond to the ACS online or by mail. Interviewers follow up with households that do not respond to the ACS online or by mail.

The reference periods for the two surveys are different. The CPS ASEC asks respondents about their income in the previous calendar year; the ACS asks about income in the prior 12 months. 

These differences often result in different national statistics for such key indicators as poverty, median income and income inequality. Despite differences between the levels of these indicators in the two surveys, the trends over time resemble each other. The following graphs compare median household income and poverty rates from the ACS with statistics from the CPS ASEC for previous years. 

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