We estimate the effect of an increase in time cost on the return behavior of blood donors. Using data from the Australia Red Cross Blood Service, we ask what happens when pro-social behavior becomes more costly. Exploiting a natural variation in which donor wait times are random, we use the...

At least one of every five marriages is consanguineous (between couples who are second cousins or closer) in the Middle East and North Africa, and the rate is higher than 50 percent in some parts of the world. Consanguineous marriage generates serious health problems for the offspring and...