Karen Grepin gives some background:
"Back in 2008, Oregon had a long waiting list of low-income adults wanting to enroll in its state Medicaid program. Given severely constrained resources it was not able to provide insurance to everyone who wanted it, so it decided to allocate eligibility to enroll into the program by lottery – it randomly assigned insurance eligibility – creating one of the most incredible opportunities to study the impact of health insurance. Period."
This study is the talk of the town amongst health / economics / research methodology wonks: here's some other commentary by Ezra Klein, David McKenzie of the World Bank, and William Savedoff of CGD.
One outstanding question to me is how on earth the Medicaid lottery happened in the first place. Yes, it was an environment of limited resources, which explains not making health insurance available to everyone who needed it in this particular timeframe. But why not choose to give the insurance to the poorest, oldest, sickest, etc? Did the officials who made that decision not have data to make such decisions? Did they think it would be less ethical? Did they think it would be more expensive to put the neediest (and most likely to use the service) on Medicaid? Did they anticipate the evidentiary value of their decision? I'm guessing it's some combination of the above, but I want to learn more.
A side note on working papers: all this talk is about a working paper (available here), which reminds me of Berk Özler's recent post on the World Bank's consistently excellent Development Impact blog criticizing the system of economics working papers. Özler cites as an example his own experience with a working paper on the role of conditionalities in cash transfer programs:
"Our findings in the March 2010 [working paper] suggested that CCTs that had regular school attendance as a requirement to receive cash transfers did NOT improve school enrollment over and above cash transfers with no strings attached. Our findings in the December 2010 version DID.... However, the earlier (and erroneous) finding that conditions did not improve schooling outcomes was news enough that it stuck. Many people, including good researchers, colleagues at the Bank, bloggers, policymakers, think that UCTs are as effective as CCTs in reducing dropout rates – at least in Malawi."
Ouch. This hits home in part because I remember reading that original working paper as part of a literature review for a grad school project on health impacts of conditional cash transfers (in which we designed a hypothetical community-based cluster-randomized trial in Bangladesh). I disseminated those results -- in part because they were counterintuitive -- to more than a few of my peers, but I didn't realize Özler had reversed his findings. If nothing else, we should take working papers that have not been through the full peer-review process with a large grain of salt.