This research project will use national longitudinal data sets of scientists and engineers between 1982 and 1989, supplemented with newly collected and constructed data measures of occupational depreciation and transferability of skills, to generate new estimates of occupational exit and reentry of scientists and engineers. The research will draw on existing theoretical models of occupational choice and occupational switching to develop econometric models of exit and reentry. Empirical techniques such as hazard rate and competing risks models will be used to estimate parameters of the models that will be used to refine projections of supply of scientists and engineers. //