The Census Bureau reports income and poverty estimates from several major national household surveys and programs. It is important to understand that different surveys and methods, which are designed to meet different needs, may produce different results.
Surveys may differ in the length and detail of questionnaires, the number of households included (sample size), and the methodology used to collect and process data. The Small Area Income and Poverty Estimates Program (SAIPE) uses data from a variety of sources to create statistical models to produce income and poverty estimates.
Background information and links to each survey or program’s website are provided below. Data users seeking assistance in selecting the data source most appropriate for their application should refer to the page on What Data Source to Use within this Guidance for Data Users section.
The CPS ASEC is the source of official annual estimates of national poverty levels and rates, as well as widely used estimates of household income, individual earnings, as well as the distribution of income. The CPS ASEC provides a consistent historical time series beginning in 1959 at the national level and can also be used to look at state-level trends and differences (through multi-year averages) going back to 1980. However, the relatively large sampling errors of state-level estimates for smaller states somewhat limit their usefulness.
The CPS is primarily a labor force survey, not an income survey, and is conducted every month by the Census Bureau for the Bureau of Labor Statistics using Computer-Assisted Telephone Interviewing (CATI) and Computer-Assisted Personal Interviewing (CAPI). The Basic CPS is used to calculate the monthly unemployment rate estimates. Supplements are added in most months; the ASEC is conducted in February, March, and April with a sample of about 100,000 addresses per year. The questionnaire asks about income from more than 50 sources and records up to 27 different income amounts, including receipt of numerous noncash benefits, such as Supplemental Nutrition Assistance (formerly known as the food stamp program), subsidized school lunches, and housing assistance.
Starting in 2006, the ACS replaced the decennial census long-form sample questionnaire. The ACS offers comprehensive information on social, economic, and housing characteristics and because of its large sample size, about 3.5 million addresses per year, the ACS is exceptionally useful for subnational analyses, serving as the best source for survey-based state level income and poverty estimates.
The ACS provides single-year estimates of income and poverty for all places, counties, and metropolitan areas with a population of at least 65,000 as well as the nation and the states, and provides estimates for all geographies, including census tracts and block groups using data pooled over a five-year period. Both single and five-year estimates are updated every year.
As with the decennial census long form, the ACS uses a paper questionnaire, although ACS respondents may also respond online or via phone.
The Survey of Income and Program Participation (SIPP) is a longitudinal survey most useful for understanding changes in monthly income and poverty status for the same individuals or households over time, typically 3 to 4 years, and for examining the nature and frequency of poverty spells. Unlike the ACS and CPS ASEC, the SIPP also permits researchers to look at estimates of income and poverty for periods of more than or less than one year, including monthly poverty rates. The SIPP is a nationally representative survey and since the 2004 SIPP Panel reliable state-level estimates are available in select states.
Whereas the CPS ASEC is a labor force survey with supplementary questions on income, the SIPP focuses on income and asks about income from up to 81 sources. The SIPP typically reports more income (and therefore lower annual poverty rates) than the CPS ASEC. The SIPP also contains detailed information on government program participation, asset-holdings, and other subject areas critical for understanding social and economic well-being.
Historically SIPP interviews were conducted in 4-month intervals, or “waves.” In the 2008 and earlier SIPP Panels, each wave included the same set of core questions about the previous 4 months, or reference period, and a set of topical questions that varied from wave to wave. The 2008 Panel had 16 waves spanning 6 years (May 2008 to November 2013). The SIPP was reengineered following the 2008 Panel, with the subsequent 2014 Panel collecting data in 12-month intervals over 4 annual waves spanning January 2013 to December 2016. In the 2014 Panel, all questions are asked in every interview. Both the 2008 and 2014 SIPP are collected using CAI (Computer Assisted Interviews) either in person or via telephone. As in previous SIPP Panels, interviewers return to the same household (not housing unit) and attempt to follow people interviewed in the first wave even if they move.
The best measure of change between 1990 and 2000 for subnational areas and for subpopulations are the comparisons of the 2000 Census long form estimates with those from the 1990 Census long form. Since the ACS eliminated the need for a long form, the 2010 Census did not provide income and poverty estimates. For small areas and subpopulations, ACS multi-year estimates are available for comparison to Census 2000 and earlier. ACS 5-year data products provide data at the census tract level which can be compared “with caution” to earlier decennial census estimates. (We suggest that comparisons focus on the direction of change, e.g. whether poverty rates went up or down, rather than the magnitude of changes).
The Census 2000 long form used a mail-out/mail-back questionnaire that was very similar that used by the ACS (asking about eight income types) in 2010. However, Census 2000 used only personal-visit follow-up using paper questionnaires while the ACS uses CATI, CAPI, internet, and other methods to improve data quality. While the ACS collects data throughout the year on an on-going, monthly basis and asks for a respondent's income over the "past 12 months," Census 2000 collected the income data for a fixed period of time -- "during 1999" (the last calendar year). In a comparison study between Census 2000 income data and the 2000 ACS, income collected in Census 2000 was found to be about 4 percent higher than that in the 2000 ACS. For more information on comparing the American Community Survey (ACS) and the Decennial Census, refer to the working paper below.
The SAIPE program produces single-year estimates of median household income and poverty for states and all counties, as well as population and poverty estimates for school districts. Since SAIPE estimates combine ACS data with administrative and other data, SAIPE estimates generally have lower variance than ACS estimates but are released later because they incorporate ACS data in the models. For counties and school districts, particularly those with populations below 65,000, the SAIPE program provides the most accurate subnational estimates of poverty. For counties, SAIPE generally provides the best single year estimates of median household income.