The Economist’s list of big economic ideas continued with its third brief talking about the Stolper-Samuelson theorem, coined by economists Wolfgang Stolper and Paul Samuelson. The theorem shed a new light on the relationship between tariffs and wages and was presented in a paper deemed “‘remarkable’ … partly because it proved something seemingly obvious to non-economists: free trade with low-wage nations could hurt workers in a high-wage country.” On the face of it, the Stolper-Samuelson theorem explains how globalisation has hurt low-skilled worker in rich economies, but it was “unable to explain why skilled workers have prospered even in developing countries, where they are not abundant.” Our favourite takeaway from the brief is this Stolper quote from 1960: “Any industry which required high duties impoverished the country and wasn’t worth having.” Next week, the series will present the famous Keynesian multiplier.