The Panel Study of Income Dynamics (PSID) is the world’s longest running household panel survey. The PSID is a longitudinal panel survey of United States families that measures economic, social, and health factors over the life course and across generations. Data have been collected from the same families and their descendants since 1968.
The PSID gathers data describing circumstances of the family as a whole (e.g., type of housing) and data about particular persons in the family (e.g., health, earnings). While some information is collected about all individuals in the family, the greatest level of detail is ascertained for the primary adult(s) heading the family (called the head and wife). The PSID has consistently achieved unprecedented response rates, and as a consequence of low attrition and the success in following young adults as they form their own families, the sample size has grown from 4,800 families in 1968, to 7000 families in 2001, to 7400 by 2005, and to more than 9,000 as of 2009. By 2003, the PSID had collected information on more than 65000 individuals. As of 2009, the PSID had information on over 70,000 individuals, spanning as many as 4 decades of their lives.
The structure of the PSID started with two distinct samples of individuals. A nationally representative sample designed by the Survey Research center became known as the SRC sample. The Census asked that a second sample of individuals, drawn from lower income levels be sampled, and this became known as the Survey of Economic Opportunity (SEO) sample. This second sample, though not nationally representative, allowed for more studies to investigate poverty in the United States. After this initial 1968 interview, families were interviewed each year until 1997. After 1997, the survey has been biannual, data being collected every two years. Over time, as individuals leave their household, they are tracked, and form a new head of household in their new residence. As time passed, the representativeness of the original sample became more and more out of line with the overall US demographic. To ameliorate the potential bias, two additional samples were added to the PSID. A third sample consisting of Latinos was added. Finally, in 1997, a new fourth Immigrant sample was added, and the other three reorganized. All three continued to be collected, but with a reduced number of households. The two "core" samples (SRC and SEO) were reduced to include 6168 families, and the Latino sample was reduced to 2000 families. To these, a new set of 441 families from the Immigrant sample created a study group capable of tracking the current demographics in the US.
The method of interviewing in the PSID has changed over time. Until 1972, interviews were done in person using paper, but after 1973 phone interviews were used. Starting in 1993, interviews were conducted using Computer Assisted Telephone (CAT) technology.
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Beginning in 1997, a new extension of the PSID started collecting information about the children of the members of the PSID. Extensive information has been collected from parents, teachers, and schools pertaining to the social, cognitive, and physical development of these children.
The PSID's information is held in many files. The main head and wife responses are held in a series of "Family Files" that are uniquely identified by a Family ID number. A smaller subset of information pertaining to individuals (whether they are a head, wife, or other family member) is contained in the cross-year individual file, and each record is uniquely identified by a Family-ID, Personal-ID pair. Many additional supplemental files are available with supplemental information that may have been collected for only one or a few years.
The PSID collects data on a wide array of social, demographic, health, economic, geospatial and psychological data. As of 2009, the 75 minute interview collected data on: (Table 1)
Many of these areas have been included in the instrument since 1968. Hundreds of additional variables that fall into other domains have been collected in various waves throughout the history of the PSID. No identifying information is distributed to data users and the identity of all respondents is held in strict confidence.
More than 2,600 peer-reviewed publications – currently 1 every 4 days -- are based on PSID data published in the fields of economics, sociology, demography, psychology, child development, public health, medicine, education, communications, and others. The PSID was named one of the National Science Foundation's "Nifty Fifty," NSF-funded inventions, innovations and discoveries that have become commonplace in our lives [1].
The PSID is conducted by the Survey Research Center at the Institute for Social Research, housed at the University of Michigan.
The main source of support for the study comes from the National Science Foundation (http://www.nsf.gov/), the National Institute on Aging ( http://www.nia.nih.gov/), and the National Institute of Child Health and Human Development (http://www.nichd.nih.gov/). There are other important sponsors of the study as well including the Office of the Assistant Secretary for Planning and Evaluation of the United States Department of Health and Human Services (http://aspe.hhs.gov/_/index.cfm), the Economic Research Service of the United States Department of Agriculture (http://www.ers.usda.gov/), the United States Department of Housing and Urban Development (http://www.hud.gov/), and the Center on Philanthropy at Indiana University (http://www.philanthropy.iupui.edu/).
The PSID has sister surveys conducted in other countries, including: