This article investigates an important but understudied phenomenon: the bureaucratic class division, which is analysed as a difference technology for envisioning, studying and managing the population. I examine a long-lived and widely spread taxonomy of the Swedish population into three social groups (Socialgrupper). Specifically, I look at how it influenced the production of statistics and knowledge about the voter during the first half of the twentieth century and higher education in the post-war welfare state era. The article understands the effects of the taxonomy as a ‘scientisation of the social’, using Lutz Raphael's term, in which fuzzy conceptual class boundaries were turned into exact classification, making it possible for different actors to act and calculate through them. The division was at the same time contested among social scientists and politicians. However, because of lack of alternatives and because it was well established, actors continued using it.