The net present value of costs and benefits from a pay-as-you-go social security system are negative for young people and positive for the elderly. If people all vote their financial selfinterest, there will be a pivotal age such that those who are younger favor smaller social security benefits...

Transplants of donated stem cells save the lives of many patients with blood diseases. Donation is somewhat painful, but rarely has lasting adverse effects. Patients can accept transplants only from donors with compatible immune systems. Those lacking a sibling match must seek donations from the...

This paper explores the quantitative relation between non random, assortative matching and the maintenance of cooperative behavior under evolutionary dynamics. We consider a population of individuals who are \hardwired" to play either cooperate or defect. They meet other individuals according to...

When academic journals were distributed only as paper editions, the obvious way for scholars to share a journal was to use the copy found on the shelves of their own university library. With the arrival of electronic access, the logistics of journal-sharing has changed radically. Physical...

This paper explores the workings of stratified societies in which there is primogeniture and where the nobility practice monogamous marriage with a double standard of sexual fidelity. We model a simple stratified society and define the reproductive values of the male and female nobility relative...

Consider a public utility that offers its service at two different times. We study the effects of a change from uniform pricing throughout the day to peak-load pricing. We show that for a utility constrained to operate with a fixed rate of return on capital, the introduction of peak-load pricing...

In most times and places, women on average marry men who are older than themselves. We propose a partial explanation for this difference and for why it is diminishing. In a society where the economic roles of males are more varied and specialized than the roles of females, it may be that the...

About 80\% of all societies recorded by anthropologists are polygynous (men have many wives). Even our own society is less monogamous than claimed. This paper attempts to explain such mysteries as why bride prices and dowries are not ``opposites'', why polygamous societies are usually...