"Economists are prone to methodological crazes. Mr Rasul recalls past paper-piles using the regression-discontinuity technique, which compared similar people either side of a sharp cut-off to gauge a policy’s effect. [..] abstracts published by the National Bureau of Economic Research, a think-tank (see chart), shows tides of enthusiasm for laboratory experiments, randomised control trials (RCTs) and the difference-in-differences approach (ie, comparing trends over time between different groups). [..] Some economists, however, argue that new methods also bring new dangers; rather than pushing economics forward, crazes can lead it astray, especially in their infancy. [..] A paper by Angus Deaton, a Nobel laureate and expert data digger, and Nancy Cartwright, an economist at Durham University, argues that randomised control trials, a current darling of the discipline, enjoy misplaced enthusiasm. RCTs involve randomly assigning a policy to some people and not to others, so that researchers can be sure that differences are caused by the policy. Analysis is a simple comparison of averages between the two. Mr Deaton and Ms Cartwright have a statistical gripe; they complain that researchers are not careful enough when calculating whether two results are significantly different from one another. As a consequence, they suspect that a sizeable portion of published results in development and health economics using RCTs are “unreliable”. [..] there is a deeper concern: that fashions and fads are distorting economics, by nudging the profession towards asking particular questions, and hiding bigger ones from view. [..] “without knowing why things happen and why people do things, we run the risk of worthless causal (‘fairy story’) theorising, and we have given up on one of the central tasks of economics.” Another fundamental worry is that by offering alluringly simple ways of evaluating certain policies, economists lose sight of policy questions that are not easily testable using RCTs, such as the effects of institutions, monetary policy or social norms."