Interindustry wage differentials in dummy variable models

Normalized interindustry wage differentials à la Krueger and Summers [Krueger, A.B., Summers, L.H., 1988. Efficiency wages and the inter-industry wage structure. Econometrica 56, 259–293] derive from a general specification of wage equations with dummy variables which cannot be directly estimated. This note illustrates how they can be obtained from the coefficients of a more specific parameterization and how their estimated variances can be transformed accordingly.