Social commentators from William Julius Wilson to Charles Murray have argued that increased sorting of people into internally homogeneous" neighborhoods,schools, and marriages is spurring long-run inequality. Cali- bration of a formal model suggests that these fears are misplaced. In order to...

Increased HIV risk creates incentives for people with low sexual activity to reduce their activity, but may make high-activity people fatalistic, leading them to reduce their activity only slightly, or actually increase it. If high-activity people reduce their activity by a smaller proportion...

Under asymmetric information about sexual history, sexual activity creates externalities. Abstinence by those with few partners perversely increases the average probability of HIV infection in the pool of available partners. Since this increases prevalence among the high activity people who...

Developing countries with highly unequal income distributions, such as Brazil or South Africa, face an uphill battle in reducing inequality. Educated workers in these countries have a much lower birthrate than uneducated workers. Assuming children of educated workers are more likely to become...

We prove that, for general demand and cost conditions and market structures, the fraction of first-best surplus that a monopolist is unable to extract in a market provides a tight upper bound on the relative distortions arising from firms' equilibrium decisions at all margins (entry and...

This paper applies principles from evolutionary biology to the study of unions. We show that unions which maximize the present discounted wages of current members will be displaced in evolutionary competition by unions with more moderate wage policies that allow their firms to live longer. This...

This paper compares retrospective and prospective analyses of the effect of flip charts on test scores in rural Kenyan schools. Retrospective estimates that focus on subjects for which flip charts are used suggest that flip charts raise test scores by up to 20 percent of a standard deviation....

It is often argued that low tax rates on owner-occupied housing divert investment from equipment. This paper demonstrates that if people are heterogeneous in their propensity to save, and if there are constraints on borrowing, favorable tax treatment of owner-occupied housing up to a certain...

Existing models of open-access resources are applicable to non-storable resources, such as fish. Many open-access resources, however, are used to produce storable goods. Elephants, rhinos, and tigers are three prominent examples. Anticipated future scarcity of these resources will increase...

The human capital of young and old workers are imperfect substitutes both in production and in on-the-job training. This helps explain why capital does not flow from rich to poor countries, causing instantaneous convergence of per capita output. If each generation chooses its human capital...