For the second time in five years, the Royal Swedish Academy of Sciences has awarded the Nobel Memorial Prize in Economic Sciences to researchers in the field of development economics. Angus Deaton, who won in 2015, has been joined this year by Abhijit Banerjee, Esther Duflo, and Michael Kremer. But the three economists this year have a very different approach to Prof. Deaton’s, although they look at similar questions of poverty, inequality, and welfare. The latter won for work that uses large survey data sets to make useful but arguable inferences. This year’s laureates, on the other hand, have reduced