|The PSID sample combines the SRC (Survey Research Center) and SEO (Survey of Economic Opportunity) samples. Both samples are probability
samples (i.e., samples for which every element in the population has a known nonzero chance of selection). Their combination is also a probability sample.
The combination, however, is a sample with unequal selection probabilities, and as a result, compensatory weighting is needed in estimation, at least for descriptive statistics.
Weight adjustments are also needed to attempt to compensate for differential nonresponse in 1968 and subsequent waves. Weights supplied on PSID data files are designed
to compensate for both unequal selection probabilities and differential attrition.
In 1997, the Panel Study of Income Dynamics (PSID) underwent several important design changes that would affect weighting. Leading these changes was a roughly 1/3 reduction in the number of PSID Core
families that will be eligible for continuous longitudinal data collection. A second important change to the 1997 PSID was the addition of a nationally representative sample of immigrant households and individuals
that would not be eligible for PSID under the original 1968 sample recruitment and sample family "following rules". The 1997 data collection year also began the transition to every second year data collection for PSID.
Finally, the 1997 PSID data collection included a special supplemental study of children age 0-12 in PSID Core and Immigrant Supplement families. Additional documentation describing the weights is provided on the