This chapter reviews the relevant findings of the empirical research that is available in the literature. The theoretical models of the experiences of immigrants in the destination country are largely developed to help explain the results of empirical analysis and stylized facts. Some of the empirical work has tried to test structural models that focus on a particular specification of a search model, testing that specification against alternatives. R. G. Ehrenberg reports simple but illustrative frequencies about unemployment rates of demographic groups in 1977. One of the most extensive tests of efficiency wage hypotheses used a rich data set on firm behavior from the Employment Opportunity Pilot Project. Turnover costs were measured directly by screening and training expenses; screening costs had a direct positive effect on the starting wage of a job, while training costs had a direct positive effect on the top wage.