Andrés Manuel López Obrador, Mexico’s president, is wildly popular, in part because of his determination to wipe out corruption. But is his crusade against graft everything it’s cracked up to be? We also look at the debate around randomised control trials, a popular but controversial tool in economics. In Congo, caterpillars are considered a delicacy. We explain why they deserve to be the next superfood. For full access to print, digital and audio editions of The Economist, subscribe here www.economist.com/radiooffer