David Leonhardt ran a survey of economics asking them "which economists were managing to do influential work on the crucial questions facing modern society."
He says there was a "runaway winner": "the small group of economists who work at the Jameel Poverty Action Lab at M.I.T., led by Esther Duflo and Abhijit Banerjee, were mentioned far more often than anyone else." Here's a short description of their work:
The basic idea behind the lab is to rely on randomized trials — similar to the ones used in medical research — to study antipoverty programs. This helps avoid the classic problem with the evaluation of aid programs: it’s often impossible to separate cause and effect. If aid workers start supplying textbooks to schools in one town and the students there start doing better, it could be because of the textbooks. Or it could be that the town also happened to hire a new school administrator.
In a randomized trial, researchers would choose a set of schools and then separate into them two groups. The groups would be similar in every respect except for the fact that one would receive new textbooks and one wouldn’t. With a test like this, as Vinod Thomas, the head of independent evaluation at the World Bank, says, “You can be much more accurate and much more clear about the effect of a program.”
An earlier post has a bunch of links to Abhijit Banerjee and some of his work. And the NYTimes article itself has a bunch of useful links.