estimates, and these two-year blocks of data are available for research purposes.
The Survey of Income and Program Participation (SIPP), conducted by the Census Bureau, is a nationally representative household sample survey of the noninstitutional population. The sample is drawn to be representative at the state level, but estimates for most states have large confidence intervals. The survey design is a continuous series of national panels, with sample size ranging from about 14,000 to 37,000 interviewed households. Although the sampling unit is the household, SIPP attempts to interview all household members age 15 and older by self-response. SIPP is designed as a panel survey of all individuals in a household, and therefore movers are followed. A new SIPP panel was fielded every three to four years over the past decade, and each panel is reinterviewed every four months. The last complete SIPP panel began in 2001 and interviewed nearly 37,000 households in a panel design of 9 waves spaced 4 months apart. The current SIPP panel, started in 2004, has approximately 43,000 households interviewed at Wave 1 (110,700 individuals of whom 29,700 are under age 18). It is scheduled for 12 waves.
SIPP is divided into core content, which is collected during each wave, and topical content, which is collected only during certain waves. SIPP collects detailed social and economic information, including program participation. It also collects some self-reported health measures, such as limitations in activities of daily living and self-assessed health status. Besides some health information, it queries income sources so that household income can be constructed. In principle, then, SIPP can be used to construct a household-level variable, such as income or wealth. However, SIPP does not obtain information on food expenditures. Low-income households are oversampled, resulting in about an 11 percent increase in the number of low-income households compared with what would be without oversampling.3 SIPP has included a subset of six food insecurity questions (but not the standard six-item set) in the adult well-being module once during each panel beginning in 1998.
Because of funding restrictions, the sample size and design of SIPP has changed often in the past. Whether it will retain a stable design and sample size is not known, but the changing design is a feature of SIPP that makes it less attractive than, say, the CPS. Moreover, the content of SIPP is decided