Despite interesting work on infectious diseases by such economists as Peter Francis, Michael Kremer, and Tomas Philipson, the literature does not set out the general structure of externalities involved in the prevention, and care of such diseases. The authors identify two kinds of externality....

Infectious diseases are transmitted from person to person or from vectors such as mosquitoes to people. The uninfected take precautions against these diseases and the infected try to mitigate their symptoms and to get cured. In doing so, people may weigh the costs of illness, prevention and...

Tax laws and administrations often treat different size firms differently. There is, however, little research on the consequences. As modeled here, oligopolists with different efficiencies determine the size distribution of firms. A government that maximizes a weighted sum of consumer surplus,...

Testing is a potentially important intervention to slow the HIV epidemic in Africa and elsewhere. Some countries in Africa have achieved high levels of testing but most have not. Cost, price, and questions of confidentiality have limited the expansion of testing. It looks possible, however, that...