Stem cell transplants save lives of many patients with blood diseases. Donation is 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 general population. The probability that two unrelated persons are compatible is less than 1/10,000. Health authorities maintain a registry of several million genetically tested potential donors who agree to donate if asked. We find that the benefits of adding registrants of every race exceed costs. We also explore the peculiar structure of voluntary public good provision that faces potential donors. (JEL D64, H41, I11)

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The plight of mixed-race leukemia patients unable to find stem cell donors with matching immunity types has received much media attention. Because of small samples, direct estimation of the distribution of immunity types for persons of mixed race has not been possible. However, because the alleles that control immunity type are located close together on a single chromosome, it is possible to estimate the distribution of types for mixed races, by using existing estimates of haplotype distributions for single races. We provide such estimates and calculate probabilities that persons of specific mixed-race combinations can find a match in the existing registry of potential donors. We also estimate probabilities that adding mixed-race donors to the registry will result in a life-saving match for a patient in need of a transplant and we compare the benefits and costs of adding new registrants of specified race or mixed race to the registry.

Formal microfinance institutions have been an important tool in the fight against poverty in developing countries, but their reach is necessarily limited. Village Savings and Loan Associations (VSLAs) are an alternative, informal mechanism for saving and borrowing that do not require external capital or ongoing financial or administrative support from a founding organization. This paper evaluates the impact of VSLAs on their members and finds that long-term members fare better along multiple economic, nutritional, and health dimensions compared to a control group of recent joiners.

Policies to reduce carbon emissions by vehicles, such as fuel economy standards and gasoline taxes, have impacts on vehicle weight and thus on safety. This paper develops a model that separately identifies the impact of vehicle weight on mortality and selection effects that impact accident propensity. The main results are that (1) the safety externalities associated with heavy vehicles are greater than the environmental ones; (2) under fuel economy standards, vehicle weights have recently decreased with little likely effect on accident deaths; and (3) similar environmental benefits could be combined with substantial reductions in deaths by implementing higher gasoline taxes. (JEL H23, D62)