Mme Duflo has, above all, developed and promoted the concept of "scientific" testing of anti-poverty programmes – what works and what doesn't but also, crucially, why things work and why they don't. She believes – and has proved – that the effectiveness of anti-poverty programmes can be explored by "random testing", in the same way pharmaceutical companies test drugs.
Esther Duflo does her research not so much in government archives and university libraries but villages in India, Ghana or Kenya. She is left wing but in a "whatever it takes" kind of way. She has spent most of the past 10 years in the US, where she is a professor at the Massachusetts Institute of Technology. Three years ago, she founded the Poverty Action Lab, to put her ideas into practice. The World Bank incorporated ideas developed by "random testing" in 87 of its programmes last year. "Some of what we prove may seem obvious but we have to overcome prejudices," she said. "Many aid organisations, for instance, believe people should not be given bribes to improve their own health."
"We have framed tests in different countries, which show that people will take, say, de-worming medicine in far greater numbers if you give them a tiny incentive, such as a kilo of beans."