We derive a structural index for labor market density based on the Ellison-Glaeser index for industry concentration. The labor market density index serves as a proxy for the number of workers that are potentially available for jobs in a particular area. The index is based on observed home-work location patterns. It is particularly useful for testing theories where the scale of the market matters. We apply this index to a standard wage equation and find that it explains almost half of the cross-region wage variance.

This study documents two empirical facts using matched employer-employee data for Denmark and Portugal. First, workers who are hired last, are the first to leave the firm. Second, workers' wages rise with seniority (= a worker's tenure relative to the tenure of her colleagues). The identification problems for the wage return to tenure are shown not to apply to the return to seniority because seniority is not a deterministic function of time. Controlling for tenure, the probability of leaving the firm decreases with seniority. The increase in expected seniority with tenure explains a large part of the negative duration dependence of the hazard. Using a variety of estimation methods, we show that a 10% increase in seniority raises your wage by 0.1-0.2%, depending on the country and the method applied. Conditional on ten years of tenure, one standard deviation of seniority raises your wage by 0.5 to 1.6 percent. Forthcoming in Econometrica.