Greater use of employment tests for selecting workers will mean that rewards for developing competencies measured by the tests will rise, increasing the supply of workers with the skills. Greater use of tests to select workers will also change the sorting of workers across jobs. The impact on total output will depend on the extent to which the developed abilities measures by employment tests have larger impacts on worker productivity in some occupations than in others. This question was examined by analyzing General Aptitude Test Battery revalidation data for 31,399 workers in 159 occupations and by reviewing the literature on how the standard deviation of worker productivity varies across occupations. The analysis found that differentials do exist and that reassigning workers who do well on a test to occupations where the payoff to talent is particularly high will increase aggregate output. The magnitude of the output effect was esimated, taking into account effects on women and minorities. Ways in which employment tests can simultaneously strengthen incentives to learn, improve sorting, and minimize adverse impacts on minority groups are discussed. Appendix A is a worker evaluation chart. Appendix B contains four tables of output variability, and Appendix C is a table of weights for revalidation data. (Contains 3 figures, 6 tables, 91 references for the text, 5 appendix references, and 57 sources for the appendix tables.) (SLD)