MIT economist Esther Duflo is the most recent recipient of the John Bates Clark Medal, arguably the economics profession's most selective award (harder to get than the Economics Nobel). She received the award for her work at MIT's Abdul Latif Jameel Poverty Action Lab, which has pioneered the use of randomized field experiments to test specific social policies, such as distributing bednets to prevent the spread of malaria or providing small financial incentives to parents to encourage them to vaccinate their children.
What is particularly appealing about Duflo's work is that it uses the strongly empirical approach that has made "Freakonomics" so popular. But she does not just wonder whether sumo wrestlers cheat or prostitutes are patriotic. She manages to ask questions that can vastly improve, even save, millions of lives in poor countries around the world.
If you have 16 minutes and 47 seconds, Duflo does a superb job summarizing some of her work in this recent video in the TED series.
Randomized field trials aren't the answer to every important question in economics. They have almost nothing to say about how we got into or how we can get out of the current world recession, for example. But, it sure is nice to see an economist ask and convincingly answer questions that really matter.