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. The CPS, however, 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 measure more completely a household’s economic status and eligibility for program benefits. To add those items to the CPS questionnaire would dilute the main purpose of that survey and unduly increase respondent 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 those 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. The 1979 ISDP Panel was a longitudinal survey in which respondents were asked about their income, labor force participation, and other characteristics. Respondents were then re-contacted every 3 months to supply information on themselves and others with whom they resided; consequently, the 3-month span was the reference period for the interview.
Creation and Evolution of SIPP
The Income Survey Development Program, conducted between 1977 and 1981, developed survey data collection strategies and instruments, as well as data processing strategies for the SIPP. The survey was originally envisioned as a jointly funded effort by the Census Bureau and the Department of Health and Human Services (HHS). Work was well underway for a February 1982 start of the survey when the HHS had to withdraw its support due to funding problems. As a result, the survey was postponed until the Census Bureau received adequate funding from Congress to conduct the survey. Interviewing for the first panel, the 1984 Panel, began in October 1983 with a sample size of approximately 26,000 designated households.
As part of our transition to the redesigned SIPP, the 1992 Panel was extended to ten waves and the 1993 Panel was extended to nine waves. We did not introduce new panels in 1994 and 1995. Before the redesigned SIPP questionnaire was introduced in the 1996 Panel, a dress rehearsal was conducted between February 1995 and September 1995. The dress rehearsal consisted of Wave 1 and Wave 2 interviews in approximately 9,000 households. 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.
Current Operations – 2014 Panel
The 2014 SIPP Panel begins in February 2014 and consists of approximately 52,000 households based on the 2010 decennial. Each household will be interviewed four times. Households will be interviewed once a year with the new SIPP Event History Calendar (EHC), as compared to the previous three times a year in previous SIPP panels. The SIPP interviews will continue to be conducted using a computer-assisted interview on a laptop computer.
The SIPP had previously been molded around a central "core" of labor force and income questions supplemented with questions designed to address specific needs in complementary subject areas. The 2014 SIPP Panel design does not contain freestanding topical modules; however, a portion of traditional SIPP topical module content is integrated into the main body of the SIPP interview. Examples of SIPP content include questions on medical expenses, child care, retirement and pension plan coverage, marital history, adult and child well-being, and others. The 2014 SIPP Panel uses an EHC that assists the respondent’s ability to recall events accurately over the longer reference period and provide increased data quality and inter-topic consistency for dates reported by respondents.
The 2014 SIPP Panel is a brand-new “wave 1” sample with new survey respondents who were not interviewed in the previous 2010-2013 SIPP-EHC field tests, which were conducted to prepare for the 2014 Panel. The 2014 SIPP Panel wave 1 will interview respondents using the previous calendar year 2013 as the reference period and will proceed with annual interviewing going forward. The 2014 SIPP Panel will use a revised interviewing method structure that will follow adults (age 15 years and older) who move from the prior wave household. Consequently, future waves will incorporate dependent data, which is information collected from the prior wave interview brought forward to the current interview.
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