There is a movement in medicine to require that applications for licenses to sell a new drug be “evidence-based.” By contrast, trained economists view their discipline as having already achieved this scientific standard. After all, they express their ideas with mathematics and arrive at quantitative estimates of implied relationships from empirical data.
But economics is not evidence-based in selecting its theoretical paradigms. Economic policy initiatives are often taken without all the empirical pre-testing that could have been done.
A notorious example is postwar macroeconomic policymaking under the radical Keynesians. The radicals relied on Keynes’s untested theory that unemployment depended on “effective demand” in relation to the “money wage,” but their policy ignored the part about wages and sought to stabilize demand at a high enough level to ensure “full” employment.
Cecil Pigou and Franco Modigliani objected that if demand were successfully increased, the money wage level would rise, catch up to demand, and thus push employment back down to its previous level. Employment cannot be sustained above its equilibrium path by inflating effective demand.