For presentation at the Fifth International Workshop on Household Survey Non-Response, September 26-28, 1994, Ottawa, Ontario.

This paper reports the general results of research undertaken by Census Bureau staff. The views expressed are attributable to the authors and do not necessarily reflect those of the Census Bureau.

Nonresponse is an important source of bias for longitudinal surveys. Longitudinal surveys like the Survey of Income and Program Participation (SIPP) require a number of interviews over a period of years. The rate of household nonresponse increases with each successive interview. The characteristics of nonrespondents are likely to differ from respondents. Consequently, the sample becomes less representative of the population over time.

The SIPP gathers information about the financial circumstances of persons, families, and households in the noninstitutionalized U.S. population. Survey participants are asked about cash and noncash income, assets, participation in government assistance programs, employment status, and other items related to their economic situation.

The sample is divided into four rotation groups of equal size. Field Representatives (FRs) attempt to obtain interviews from sample households from one rotation group each month. Each interview of all four rotation groups is called a wave. Starting with the 1984 panel, a panel has typically been introduced each year through 1993. The number of sample households and waves vary with each panel. The 1987 panel, for example, was interviewed for seven waves and started with 12,500 interviews of households in wave 1.

Starting with the 1996 panel, we plan to introduce panels of approximately 50,000 households every four years. The size of 1996 panel will likely be cut to around 45,000 households for budgetary reasons. Sample households will be interviewed every 4 months for about 4 years.

Researchers (Short and McArthur 1986; Petroni 1987; and others) have documented the potential for attrition bias through differential attrition. Other researchers have found differences between estimates of some items from SIPP data and estimates from other sources. For example, marriage rates (Hernandez, 1989) and migration (DeAre 1990).

From the beginning of the SIPP, the Census Bureau has conducted research to measure bias, reduce nonresponse, and better compensate for nonresponse in weighting. Results from three such efforts: Allen and Petroni (1994), Folsom and Witt (1994), and Rizzo et al. (1994); each focusing on alternative weighting adjustments for nonresponse, have recently been reported. This paper provides a short summary of these studies.