Kessler, Judd B. and Alvin E. Roth, Organ Allocation Policy and the Decision to Donate," June 2010. (As an added bonus, Judd is on the jobmarket this year.)
Here's the abstract: "Organ donations from deceased donors (cadavers) provide the majority of transplanted organs in the United States, and one deceased donor can save numerous lives by providing multiple organs. Nevertheless, most Americans are not registered organ donors despite the relative ease of becoming one. We study in the laboratory an experimental game modeled on the decision to register as an organ donor, and investigate a variety of strategies for increasing the donation rate. We find that an organ allocation policy giving priority on waiting lists to those who previously registered as donors has a significant positive impact on registration.
And this is from the concluding section
"Before further considering the benefits of the priority rule, it is worth noting that there are other ways to change policy that could positively affect the number of registered organ donors. For example, one proposal that has received a good deal of attention would change the current “opt in” registration method used in the United States to an “opt out” system in which everyone is presumed to be a donor unless he or she actively indicates otherwiseAnother proposal, “mandated choice” would require everyone (e.g. who applies for a driver’s license) to specifically indicate whether they wished to be a donor or not. We want to briefly argue here that the priority rule that we consider may create a more direct link between registration as an organ donor and subsequent successful organ recovery and transplantation than policies that change the procedure by which individuals register as organ donors.