A substantial number of employees work additional noncontract hours for no pay. The authors advance several economic explanations for this phenomenon. Empirical work is based on the U.K. Labour Force Survey for 1993/94. The authors establish the quantitative importance of unpaid work on overtime hours and hourly earnings for both males and females. They demonstrate, via Mincer wage growth equations, that accounting for unpaid work leads to significantly revised estimates of returns to education, experience, and tenure. The authors test a number of hypotheses arising from their economic discussion using Tobit regressions of unpaid overtime. For comparative purposes, the authors also estimate equations of paid overtime. Copyright 1999 by The London School of Economics and Political Science
