Unfortunately, most of the available longitudinal data sets are poorly
suited to analyzing the components of intra-year variation in labor supply.
Typically, these data sets are based on annual questionnaires that inquire
about weeks of work and usual or average hours per week during the previous
12 months. The recently released Survey of Income and Program Participation
(SIPP) is an important exception. Unlike other data sets, the SIPP
questionnaire is administered every four months. The SIPP panel therefore
provides a unique opportunity to analyze the composition of higher-frequency
changes in labor supply.