As well as his specific contributions to our understanding of the world, Mr Deaton offers three lessons to aspiring economists. First, the theory should tally with the data—but if not, then do not despair. Puzzles and inconsistencies help to prompt innovation. Second, the average is rarely good enough. It is only by understanding differences between people that we can understand the whole. Finally, measurement matters. In the words of Mr Deaton, “progress cannot be coherently discussed without definitions and supporting evidence”. In the words of Mr Muellbauer, Mr Deaton’s win is “a triumph for evidence-based economics”.