The Social Security Administration (SSA) produces a popular statistical series, Income of the Population 55 or Older, to meet the demand for statistics on the receipt of income from various sources, income distributions, aggregate income, and poverty. This statistical series is based on data from the March Supplement to the Census Bureau's Current Population Survey (CPS).1 These statistics are affected by the selection of the CPS as its data source.
This article provides insight into how the data collected in the CPS affect measures describing the economic well-being of the elderly. Because Income of the Population 55 or Older is based on a survey, the accuracy of its statistics is dependent on the willingness and ability of CPS respondents to answer survey questions accurately. Different surveys have different strengths and weaknesses, and one method of assessing the differences is to compare one survey's data with those of other surveys. The article also compares statistics calculated using the CPS with another Census Bureau survey that is particularly strong at measuring income-the Survey of Income and Program Participation (SIPP).
Another method for determining the accuracy of survey data is to compare them with administrative data. The Census Bureau in collaboration with SSA has matched administrative records for the Social Security and Supplemental Security Income (SSI) programs to the SIPP and selected years of the CPS. Although administrative data are not used in Income of the Population 55 or Older, they are used in parts of this article to evaluate the accuracy of the reported data for Social Security benefits and Supplemental Security Income in both the CPS and the SIPP.
First, the major features of the CPS and SIPP are outlined, and a description of SSA's administrative data available to be matched to those two surveys is also given. The article then compares estimates from the SIPP and CPS of the proportion of the elderly receiving income from various sources. Next, administrative data for Social Security benefits and SSI are used to evaluate the accuracy of the estimates derived from the surveys. Finally, the conclusion discusses the tradeoffs involved in selecting a data source.
Data Sources Used in this Analysis
The Social Security Administration has been producing two series of publications on the income of the elderly and near-elderly- Income of the Population 55 or Older (IP55), since 1976 and Income of the Aged Chartbook, since 1990. Both series are derived from the March Supplement to the Current Population Survey, which is conducted annually by the U.S. Census Bureau. Another Census survey that asks more detailed questions regarding income is the Survey of Income and Program Participation. This analysis uses income data for 1996 because the SIPP match rate to administrative data declined considerably for the 2001 panel.2
Depending on their respective purposes, surveys may differ in many ways: the subjects covered, the questionnaire length and detail, the frequency of interviews, and the sample of the population surveyed are a few of the dimensions along which surveys may vary. The following descriptions of the CPS and SIPP outline some of the broader differences between the surveys that may influence differences in the statistics produced using their data.
Current Population Survey. The CPS is a monthly survey conducted by the Census Bureau and sponsored jointly with the Bureau of Labor Statistics. The CPS is a representative sample of the "civilian noninstitu-tional population." The survey has been conducted for more than 50 years and is used for official monthly unemployment and labor force statistics. Annual income data have been collected in the March Supplement since 1948, with information gathered concerning income received during the previous calendar year for approximately 35 cash and in-kind sources. …