The aim of this investigation is to explain present and historical differences in the Swedish and Danish unemployment rates between 1976 and 2005 with a broad framework, making use of neoclassical and post-keynesian economic theory. The influence of the rate of investment to GDP, and various institutional factors are assessed in quantitative analysis. It is suggested that the crude answer of the question asked in the title, “What is it that Denmark does that Sweden does not?”, is that Denmark invests. This investigation suggests accordingly that the main reason of the relative labour market success during the 90’s in Denmark was a rising, and rapidly recovering, rate of investment to GDP, and perhaps not primarily its flexible labour market...