Estimating the Number of Individuals in the U.S. Without Health Insurance. Introduction

01/31/2005

As policy makers continue to search for solutions to the problem of the uninsured, analysts have sought ways to better understand who comprise the uninsured population and how this population has changed over time. Although there are multiple sources of data on the uninsured, the Census Bureau’s Annual Social and Economics Supplement (ASEC)2 to the Current Population Survey (CPS) is often the main focus of analytic work. Some of the reasons for this are: it is the most widely cited source of data, it has the largest sample size of any major survey with data on the uninsured, it can be used for state-level analysis, and it contains detailed data allowing for analysis of the uninsured by income level (a significant factor given how most proposed solutions to the uninsured problem are means-tested in some manner). However, one factor that has complicated the analysis of the uninsured is that this supplement to the CPS has changed considerably over time, making longitudinal analysis less reliable.

These survey changes create sources of discontinuity in the CPS data that need to be adjusted for over time in order to allow policymakers to understand the trends in both direction (increases or decreases in coverage) and level (how many people are insured or uninsured). As a result, the Office of the Assistant Secretary for Planning and Evaluation (ASPE) has been working with Actuarial Research Corporation (ARC) to refine the CPS time series and account for other CPS data issues.

This report discusses estimates of the number of uninsured from the unadjusted CPS, looks at the CPS in the context of other surveys that estimate the number of uninsured, and discusses revisions to the survey and how we have adjusted for them in order to have a consistent time series. Finally, we will look at how a particular limitation with the CPS estimates (the count of persons with Medicaid) can be adjusted for, and how this affects the estimate of the uninsured.

How Our Approach is Different: The focus of this report is covered lives, e.g. the counts of people who have or do not have health insurance coverage during different time intervals or at specific points in time. The number of uninsured reported will vary substantially depending on the approach selected. The report does not address changes in health insurance benefits, shares of premiums paid by employers and employees, or other changes in the health insurance market that occurred over the period studied. We concentrate on data from the last nine years, starting with the March 1995 CPS and ending with the most recent (March 2004) year available. We begin at March 1995 due to the many major changes in the survey that occurred that year and which affect the insurance estimates from that point forward. In addition, we have also applied our methodology back to CY 1989 (March 1990) in order to look at changes in insurance over a longer time period. Due to the many improvements that occurred with the March 1995 survey, we are more confident in our estimates from that point forward. Our methodology is explained below, and in more depth in the methodological appendix accompanying this paper.


2The Annual Social and Economics Supplement to the CPS was formerly known as the March Demographic Supplement and is also known as the “March CPS.” Data on the ASEC is collected in March and insurance information refers back to the prior calendar year (for example the 2003 ASEC is collected in March 2003, with insurance information from CY 2002).

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