Firm Heterogeneity and Worker Self-Selection Bias Estimated Returns to Seniority

I develop a model under which workers with different marginal productivities self-select into firms based on the firm's seniority reward policy. I show how this may bias upwards the estimates of returns to seniority in cross-sectional and even some longitudinal studies, when differences in workforce composition are ignored. I develop a new estimator of true returns to seniority and empirically test the implications of the model. I show how several previous estimation strategies over-estimate returns to seniority, particularly in firms that offer zero or negative returns to job seniority, using a large longitudinal sample of French firms and workers.
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