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...

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 self-interest, 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...