Even as the face of SIPP has changed over the years, its purpose has remained the same: SIPP provides high-quality data related to income, labor force participation, social program participation and eligibility, and general demographic characteristics to measure the effectiveness of existing federal, state, and local programs. SIPP also serves to estimate future costs and coverage for government programs and provide statistics on the distribution of income and measures of economic well-being in the country.
The main objective of the SIPP has been, and continues to be, to provide accurate and comprehensive information about the income and program participation of individuals and households in the United States. The survey’s mission is to provide a nationally representative sample for evaluating: 1) annual and sub-annual income dynamics; 2) movements into and out of government transfer programs; 3) family and social context of individuals and households; and 4) interactions among these areas.
Until the advent of SIPP, the major source of data on income and program participation was the Current Population Survey’s (CPS) March Income Supplement. The CPS continues to be the source of all official income and poverty statistics published by the Census Bureau; however, the CPS is designed primarily to obtain information on employment. Because income measurement was never the primary purpose of the CPS, it has certain gaps in that area. The CPS does not capture the impact of changes in household composition during the year, nor does the survey explicitly measure periods of program participation. Additionally, the CPS does not collect data on assets and liabilities, which are needed to completely measure a household’s economic status and eligibility for program benefits. To add those items to the CPS questionnaire would dilute the focus of the survey and unduly increase survey participant burden. Finally, the CPS is designed to be a cross-sectional survey. During the 1970s, the increasing size of government programs and their interactions with the labor market led to a need for longitudinal data.
To address these data issues, the Department of Health, Education, and Welfare (HEW) initiated the Income Survey Development Program (ISDP) in the late 1970s. In developing ISDP content and procedures, HEW focused on questionnaire length, length of reference period, and linkage of survey data to program records. Much of the work centered around four experimental field tests that were conducted in collaboration with the Census Bureau. These tests examined different concepts, procedures, questionnaires, and recall periods.
Based on experience obtained in the ISDP, planning began for implementation of a new survey known as the Survey of Income and Program Participation. The primary goals in designing SIPP were to improve reporting of income and other program-related data in a way that would allow the analysis of changes over time at a micro-level. The design also had to accommodate the collection of a large quantity of information in a flexible manner that allowed some information to be collected more frequently than other information. These goals were met principally by using a survey design in which the same people are interviewed more than once. Persons at households selected for a sample panel are interviewed about their income and other topics once every 4 months for approximately 2 1/2 years.
The first SIPP interviews were conducted in October of 1983 with a sample of over 20,000 households. At each interview, survey participants were asked to provide information covering the 4 months since the previous interview. The design of SIPP called for a nationally representative sample of individuals 15 years of age and older in households in the civilian non-institutionalized population. Those individuals, along with others who subsequently lived with them, were to be interviewed once every 4 months over a 32-month period.
In 1990, the Census Bureau asked the Committee on National Statistics (CNSTAT) at the National Research Council to undertake a comprehensive review of SIPP. The resulting report, The Future of the Survey of Income and Program Participation (Citro and Kalton, 1993), summarized the first 9 years of SIPP and provided recommendations for the future of the survey. Some of those recommendations were implemented in what is known as the 1996 redesign.
One of the goals of the 1996 redesign was to improve the quality of longitudinal estimates in order to provide better information for policy makers. Specific changes to the survey included:
Delayed by the 1995 and 1995-1996 federal government shutdowns and related furloughs, instead of in February 1996, the first interviews of the redesigned SIPP began in April 1996. Later in 1996, Congress passed the Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA). That law significantly altered the nature of public transfer programs, shifting more responsibility to state governments, establishing new eligibility rules for a number of programs, and setting limits on who could receive benefits. The existing welfare program, Aid to Families with Dependent Children (AFDC), was replaced with a new program, Temporary Assistance for Needy Families (TANF). Those changes came after interviewing for the 1996 Panel had already begun with a questionnaire designed for the array of transfer programs that existed before PRWORA was enacted. To accommodate program changes brought about by PRWORA, the Census Bureau began adapting transfer-program questions to reflect the current situation.
In 1996, the SIPP Executive Committee established the Continuous Instrument Improvement Group (CIIG), consisting of staff from numerous divisions, whose task was to review and improve the SIPP core instrument. The CIIG generated an extensive set of recommendations including the need for thorough and rigorous testing, which led to the creation of a methods panel separate from the production survey. The methods panel project consisted of a small survey separate from the SIPP 2001 panel, which was experimentally designed to support rigorous testing of new alternative instrumentation. Testing took place between 1999 and 2003, including three field tests in 2000, 2001, and 2002. Field tests included a test instrument (consisting of CIIG's recommendations) and a control instrument (the SIPP 2001 production instrument). Results were then compared and analyzed, and the final instruments were delivered for implementation in the 2004 Panel.
In 2006, the U.S. Census Bureau began its second major redesign of the SIPP that became known as ‘Re-engineered SIPP’ (or ‘Re-SIPP’). The catalyst for this redesign was SIPP’s imminent cancellation. Though SIPP was saved by support from various stakeholders, major changes were deemed necessary. The goals of the redesign were to reduce costs and respondent burden and to improve data quality and timeliness. The new survey instrument, called SIPP-EHC, was a complete redevelopment of the survey instrument built around changing the survey reference period from four months to one year. The new design also introduced an Event History Calendar (EHC) that assists the respondent’s ability to recall events accurately over the longer reference period. The EHC also provides increased data quality and inter-topic consistency for information reported by survey participants. The first interviews with this new instrument were conducted in February 2014. SIPP data since 2014 are based on this design.