Estimating the Number of Americans without Health Insurance: Not a Simple Count

In any year, reports on the number of Americans without health insurance show varied numbers. Government estimates of the number of uninsured in 2003 ranged from 19 million, reported in the Survey of Income and Program Participations, to 45 million in the Current Population Survey (CPS).¹ This discrepancy in reporting is partly a result of differing definitions of uninsurance, the fluidity of the uninsured populations, and the difficulty in tracking individuals who were uninsured for an entire year. For example, though the CPS attempts to measure the number of people who lack health insurance for an entire year, its estimate might more realistically report the number of people who are uninsured at the specific time they respond to the survey.²

Although experts often disagree on which data and methods are best to estimate the number of uninsured, determining both the number and composition of the uninsured population is necessary to inform policy debates and shape social programming.

Recent research commissioned by HHS Assistant Secretary for Planning and Evaluation Michael O'Grady suggests that the number of Americans without health insurance may be as much as 20 percent less than some studies have suggested.³ The CPS, the most frequently cited source of data on the uninsured, reported that 15.6 percent of the population, were without health insurance in 2003.⁴ However, independent analyses have found that the CPS may be undercounting the number of beneficiaries enrolled in Medicaid or with privately purchased health insurance. The Actuarial Research Corporation (ARC) and the Urban Institute worked with HHS to address the Medicaid undercount in the CPS data and incorporate Medicaid undercount adjustments into simulation models. ARC estimated more than 9 million Medicaid beneficiaries reported that they were uninsured on the CPS survey, while the Urban Institute estimated the Medicaid undercount at 3.6 million.⁵

Typically, surveys like the CPS report lower levels of public program enrollment than counts based on administrative data adding to confusion about the number of uninsured. Inaccurate reporting on the CPS may occur because respondents fail to understand their Medicaid eligibility status or are unaware of their enrollment in public health programs. However, Minnesota 's Medicaid Undercount Experiment, based on a survey of Minnesota Health Care Program (e.g., Medicaid and MinnesotaCare, a program covering Minnesota residents who do not have access to affordable health insurance ) enrollees, shows that known Medicaid enrollees responded accurately to survey questions about their health insurance status.⁶ Findings suggest that, for the most part, Medicaid enrollees may know whether or not they have insurance and whether they have public or private coverage, but are less sure which public program they are enrolled in.

To examine the accuracy of survey responses and provide a better methodology for adjusting counts of Medicaid recipients and the uninsured in surveys, HCFO grantee Kathleen Call, Ph.D., is replicating the Medicaid Undercount Experiment in three states, California, Florida, and Pennsylvania. Dr. Call and her colleagues are also exploring potential sources of miscounts in administrative data as well as the comparability of these two data sources (survey and administrative). Since survey estimates of the uninsured play a central role in setting policy and allocating resources, the results of this study would improve the confidence with which these survey results are used.

In a recent workshop co-sponsored by HCFO and the State Health Access Data Assistance Center (SHADAC), researchers and policymakers met to discuss initial findings from the Survey and Administrative Data Sources of the Medicaid Undercount studies. The workshop featured new data from several ongoing projects including presentations from Call's HCFO-sponsored survey. For the most part, early evidence from the case studies indicates that though there is a slight Medicaid undercount, it does not seem to significantly bias counts of the uninsured. Findings also suggest that though a small number of Medicaid beneficiaries report that they have no health insurance on surveys like the CPS, most report they have coverage, although some indicate the wrong type of coverage. These results raise concerns about the merits of recoding the responses of those who respond in surveys that they have no insurance to Medicaid, and point to the remaining amount of work to be done in the search for a useful and widely accepted number of uninsured.

Read More about Dr. Call's HCFO Project.

Title: The Medicaid Undercount: Real or Perceived Bias in Estimates of Coverage in General Population Surveys
Institution: University of Minnesota
Time: December 2003 - December 2005
Principal Investigator: Kathleen Thiede Call

Other HCFO-Funded Work on the Uninsured:

Title: The Dynamics of Health Insurance Coverage: 1996 to 2000
Institution: The Urban Institute
Time: September 2003 - February,2005
Principal Investigator: Linda Blumberg, Ph.D.

What are the dynamics of health insurance for children and adults under age 65 from 1996 to 2000, a period characterized by the implementation of national welfare reform, SCHIP, and an economic boom? The researchers will document the patterns of insurance coverage and public program eligibility, estimating the impact of the implementation of SCHIP on insurance coverage for eligible children and previously Medicaid eligible children, and assessing the extent to which the economic expansion affected the insurance coverage of previously uninsured adults. The objective of this project is to inform the design of more effective strategies to maintain or increase insurance coverage and to understand better the determinants of participation and crowd-out that can be useful when considering coverage expansions. The findings will also help to better predict the implications of reductions in coverage resulting from states' efforts to balance their budgets or in the economic context of a recession.

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Title: Effects of the Balanced Budget Act and Market Forces on the Health Safety Net
Institution: Virginia Commonwealth University
Time: September 2001 - August 2004
Principal Investigator: Gloria J. Bazzoli, Ph.D.

How has the Balanced Budget Act of 1997 and other major trends (e.g., growth in the number of uninsured, growth in private managed care, and Medicaid managed care) affected the U.S. hospital safety net? Researchers at Virginia Commonwealth University examined the structural, operational, and outcome-related impacts of the changing environment. Specifically, they studied four research questions: 1) How are recent changes in hospital reimbursement through BBA 1997 and the Balance Budget Refinement Act of 1999 (BBRA) interacting with other market and policy forces to affect the role and involvement of hospitals in local health safety nets? 2) How are current financial pressures affecting the operational decisions of safety net hospitals related to patient care staffing and the intensity of services provided? 3) How are current financial pressures and operational decisions in response to these pressures affecting the quality of patient care within safety net hospitals? 4) As BBA and BBRA provisions are reassessed and revised over the next two years, what potential effects would these revisions have on hospital involvement in safety net care, their operational decisions, and ultimately the quality of care that patients receive? The researchers found that in the 1990s, larger and more advanced hospitals became members of health systems. Findings also suggest that safety net hospitals were more likely to participate in networks when hospitals faced less market pressure and few unaffiliated hospitals remained unaffiliated with the system. This project provides information to policymakers and hospital administrators about the effects on the safety net of changes in reimbursement to help them formulate policy that addresses potential unintentional consequences of the BBA.

Grantee Publications: U.S. Hospital Industry Restructuring and the Hospital Safety Net ( http://www.hcfo.net/grantees/GranteePub.cfm?id=%20277 )

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¹ "Coverage & Access: Number of Uninsured Might Be Overstated, New Research Suggests," The Henry J. Kaiser Family Foundation, Kaiser Daily Health Policy Report, April 25, 2005. http://www.kaisernetwork.org/daily_reports/rep_index.cfm?hint=3&DR_ID=29604

² "How Many People Lack Health Insurance and For How Long?" Congressional Budget Office, Economic and Budget Issue Brief, May 12, 2003. http://www.cbo.gov/showdoc.cfm?index=4211&sequence=0

³ "Number of Uninsured May be Overstated, Studies Suggest," Los Angeles Times, April 26, 2005. http://www.latimes.com/news/nationworld/nation/la-na-uninsured26apr26,1,2553979.story

⁴ DeNavas-Walt, C. "Income, Poverty, and Health Insurance Coverage in the United States : 2003," U.S. Census Bureau, August 2004. http://www.census.gov/prod/2004pubs/p60-226.pdf

⁵ "9 Million Fewer Uninsured?" Meeting Summary, American Enterprise Institute for Public Policy Research, April 2005. http://www.aei.org/events/filter.all,eventID.1042/summary.asp

⁶ "Do National Surveys Overestimate the Number of Uninsured? Findings from the Medicaid Undercount Experiment in Minnesota," State Health Access Data Assistance Center Issue Brief, Issue 9, January 2004. http://www.shadac.org/publications/issuebriefs/IssueBrief9.pdf