The effect of paying the travel expenses of living kidney donors: Schnier et al. on NLDAC

The National Living Donor Assistance Center (NLDAC) can only give a very little money to economically deprived kidney donors who are donating to economically deprived recipients. But that has an effect. Here's a recent paper:

SUBSIDIZING ALTRUISM IN LIVING ORGAN DONATION
Kurt E. Schnier, Robert M. Merion, Nicole Turgeon and David Howard, Economic Inquiry
Version of Record online: 30 AUG 2017
DOI: 10.1111/ecin.12488

Abstract
The current supply of deceased donor organs is insufficient to meet the growing demand for transplantable organs. Consequently, candidates for kidney transplantation are encouraged to find a living donor. In 2008, the Department of Health and Human Services began to reimburse donors' travel-related expenses via the National Living Donor Assistance Center (NLDAC). Using variation in transplant centers' applications for donor assistance, we use a difference-in-difference model to estimate the relationship between the NLDAC and living donor kidney transplants. We find that among participating transplant centers, the program increased the number of living donor kidney transplants by approximately 14%.