The Definition of Part-Time Employment: A Switching Regression Model with Unknown Sample Selection

Rejecting the standard less-than-thirty-five-hours-per-week categorization of part-time workers, this paper offers an empirically-justified definition of the part-time employed. The definition is based on the distinction through wage payments that employers make between a high-hours (full-time) and a low-hours (part-time) group of workers. A switching regression model of wage equations with deterministic, but unknown, sample selection is estimated resulting in a significant split between high-hours and low-hours workers that is higher than the standard definition. Wage differentials are calculated and decomposed, and estimates from the structural choice model are presented. Copyright 1991 by Economics Department of the University of Pennsylvania and the Osaka University Institute of Social and Economic Research Association.