I’m a little late to point this out but this paper is the most important economics paper of the year. It uses a randomised experiment in Oregon (and kudos to the state of Oregon to being farsighted enough to provide both it and the data) to measure the impact of providing health insurance to low income households. The study was conducted with scientific transparency never before seen in economics or, possibly, social science — right down to committing to regressions the research team would run prior to receiving the data.
The measured effects are huge — most notably on happiness. On one reading it is as clear a case for social insurance as any empirical case has been made for, say, early childhood development. Here is a discussion by Ray Fisman.