Survey of Income and Program Participation

An important type of nonsampling error that has been identified in the Survey of Income and Program Participation (SIPP) is known as the seam effect. The SIPP is a panel survey with an interval of four months between waves, but with information on many income sources being collected on a monthly basis. A common finding has been that more month-to-month changes in recipiency of most income types occur when the data are collected in different waves (e.g., between months 4 and 5, or 8 and 9) than when the data are collected in the same wave (e.g., months 1 and 2, 3 and 4, 6 and 7). This finding, termed the seam effect, can affect the measurement of gross change and measures of durations of spells on social programs. It has been a central focus of the research conducted under the JSA. The report comprises three chapters. The first, by Kalton and Miller, examines the seam effect in relation to the monthly amounts of Social Security payments reported in the first twelve months of the 1984 SIPP Panel. The analyses take advantage of a known 3.5% increase in Social Security payments that occurred in January 1984 to compare the characteristics ofrecipients who reported an increase that month with those of recipients who failed to do so. Chapter 2, by Hill, investigates the seam effect for several characteristics in the 1984 SIPP Panel, and also for characteristics in the Panel Study of Income Dynamics (PSID). The conclusion reached is that the seam effect in PSID is at least as severe as that in SIPP. The paper also reports findings on some of the correlates of the propensity to provide inconsistent reports which give rise to the seam effect. As part of the SIPP quality control program, a small subsample of SIPP respondents is reinterviewed each month. The aim is to evaluate and to indicate when retraining is required. Although the reinterview program is not designed to provide evidence on nonsampling errors, it has the potential to do so. Chapter 3, by Hill, explores the use of the reinterview data for investigating nonsampling errors in the SIPP. The chapter demonstrates that the reinterview data can be useful for this purpose, and suggests some changes to the program that would improve its utility for nonsampling error research.