Despite social policy being one of the most quantified policy fields today, there is no singular indicator or set of indicators of social policy quality or performance on the global level that is universally accepted and influential, comparable to GDP in the economy. The article analyses and explains the unsuccessful indicatorisation in the ILO’s International Survey of Social Services of the interwar years. During this first elaborate study of social policies worldwide by an international organisation, difficult issues of defining, comparing, and quantifying social policy had to be solved for the first time. Theoretically, a sociology of knowledge approach on indicatorisation is utilised that highlights how social policy was questioned and evaluated. This illustrates the demanding work of comparing including a politicized knowledge production, identifying conditions and hindrances of defining and quantifying the 'social'. It is observed that different interests of participants, epistemic cultures, and practices, as well as bureaucratic procedures resulted in the mere inclusion of a provisional indicator of cost and little quantified data in the final Survey. Empirically, the article relies on an in-depth analysis of historical ILO documents.