Tied Wage-Hours Offers and the Endogeneity of Wages

Abstract

In the standard model of labor supply, each worker is a price taker,where the relevant price is an hourly wage rate which is fixed in the short run, and which does not depend upon the number of hours supplied. With this basic assumption, the wage can be regarded as exogenous for the purpose of estimating a labor supply function. This paper proposes and implements a pair of tests for the exogeneity of wages in a longitudinal labor supply model, and for the particular failure of exogeneity associated with jobs that offer wage-hour packages.The first test is very simple -- it amounts to a test of whether hours Granger -- cause wages at the individual level. The second test involves a simultaneous estimation of labor supply and wage offer equations. Both tests indicate that the offered wage is related to hours worked, though the offer locus is, for this sample, very flat. The principal conclusion is that labor supply equations cannot properly be estimated in isolation from the process generating wages, even when long time series are available on a sample of individuals.