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Current Population Survey (CPS) will Serve as Primary Source of 2020 State-level Data on Health Insurance

On September 14, the U.S. Census Bureau released 2020 health insurance estimates from the Current Population Survey (CPS). These data will serve as one of the only sources of 2020 state-level health insurance as the Census Bureau will not be releasing its typical 1-year estimates from the 2020 American Community Survey (ACS) due to impacts of the COVID pandemic that resulted in substantially lower response rates and nonresponse bias.

SHADAC typically relies on the ACS to study state and sub-state (e.g., state coverage by race) health insurance trends and posts detailed state estimates on State Health Compare. However, because the ACS data are not being released this year, we recommend that analysts instead use the CPS and have posted 2020 estimates from the CPS on State Health Compare for analysts and policymakers that need 2020 state-level information on coverage. This blog provides an overview of important differences between the two surveys for those using CPS estimates in place of the ACS this year.

Key differences between CPS and ACS
There are some critical differences between the CPS and ACS, and it is important to understand these differences when interpreting results.

Sample size
Perhaps one of the most critical differences between the ACS and the CPS for analysts and policymakers interested in estimates at the state, and more granular levels of geography or subpopulations, is sample size. The ACS has significantly more sample than the CPS; over 2 million households in 2019 compared to just over 94,000 in the CPS. Sample size is the primary reason that SHADAC typically uses the ACS to produce estimates of coverage for State Health Compare. As we note in our blog outlining results from the CPS, relying on the CPS means that we are unable to produce as many subpopulation estimates within states as we do with the ACS. In addition to limiting the estimates that can be produced, the smaller sample size of the CPS also results in less precision, even for estimates that the sample size does support.

Conceptual differences in the definition of the uninsured
The CPS estimates presented above and on State Health Compare reflect insurance status of respondents for the entire calendar year of 2020. In contrast, the ACS collects information at a “point in time” when the survey was conducted. As a result, estimates of uninsurance in the CPS are lower than the ACS, because people who had coverage at some point in the prior calendar year are not considered uninsured. The ACS, on the other hand, captures a cross-section of people who are uninsured at the time the survey was conducted, some of whom were not uninsured for the entire year. These differences are important, but it is also helpful to note that the surveys have historically demonstrated similar national trends over time, and the patterns across states are consistent in that states with low uninsurance levels have low levels in both surveys, and states with high levels have high levels in both surveys, and so on. For more detailed comparisons across surveys in prior years, see SHADAC’s “Comparing Federal Government Surveys That Count the Uninsured” brief.

Reference period
As discussed above, the CPS asks about coverage for the entire previous calendar year. The survey is fielded in February through April of each year, with respondents being asked to report their coverage for a time period as long as 16 months prior to the interview. The ACS collects information about current coverage only. Differences in the length of time for which respondents are being asked to recall their insurance coverage status can result in differences in measurement error across the surveys.

Breadth of Related Measures
Another important difference between the two surveys is the breadth of related content. The ACS’ main focus is broad demographic information, with just one question on health insurance. While the rich demographic information supports examination of the uninsured and the exploration of coverage by individual characteristics (e.g., social determinants of health) it has limited health policy applications. The CPS, on the other hand, contains a range of measures that are broadly relevant to health policy, such as medical out of pocket spending, health status, and eligibility for employer coverage. This means that the survey can be used to answer more complex research questions about the interactions between coverage and these related outcomes than could be supported through analysis of the ACS. The CPS also collects much more detailed information on income and employment than the CPS.

Looking Ahead
The CPS provides a good alternative for those that usually rely on state-level estimates of coverage from the ACS for analysis and planning. However, the data source does have some limitations, particularly for those seeking more granular estimates by geography and subpopulations within states. SHADAC is available to provide technical assistance to states that are seeking additional guidance on potential data sources to leverage for answering these questions in 2020. We will also be tracking the Census Bureau’s release of the 2020 1-year experimental ACS data, which are expected by November 30 of this year.

References
U.S. Census Bureau. (2016, May 16). Fact sheet: differences between the American Community Survey (ACS) and the Annual Social and Economic Supplement to the Current Population Survey (CPS ASEC). https://www.census.gov/topics/income-poverty/guidance/data-sources/acs-vs-cps.html

State Health Access Data Assistance Center (SHADAC). (October 2020). Comparing federal government surveys that count the uninsured: 2020. https://www.shadac.org/publications/comparing-federal-government-surveys-count-uninsured-2020

Stewart, A. (2021, July 30). Census Bureau announces major changes to 2020 American Community Survey (ACS) data release. State Health Access Data Assistance Center (SHADAC). https://www.shadac.org/news/changes-to-2020-acs-data-release-US-Census

Stewart, A. (2021, August 27). New SHADAC brief looks at changes in federal surveys during COVID pandemic. State Health Access Data Assistance Center (SHADAC). https://www.shadac.org/news/new-shadac-brief-looks-changes-federal-surveys-during-covid-pandemic