Another feature of panel data for research on aging is the length of the panel period. In this dimension the NLS Mature Women and the PSID are longer than the other studies. The RHS is confined to a ten year panel period, the LSOA to a six year panel period, and both surveys have been discontinued. The SIPP began in 1984 but panels only extend 36 to 48 months and are replaced annually. The other studies are biennial with some annual data collection.
Sample size is also a consideration.
The SIPP sample size is large, especially if panels are combined, but the lack of focus on the older cohorts greatly reduces its efficiency for analysis of issues of aging and retirement. For some purposes it is important that some special groups be present in the sample in sufficient numbers to allow independent analysis. Similarly, until 1998, PSID contained a rich oversample of individuals whose families were initially poor in 1996. No African Am. No No Low Income African Am.