“The one big challenge is definitely measurement!”

This article explores the micropolitics of measurement in social investment programs. Such programs represent an economization of social problems as they wed social returns, like increased wellbeing, with financial returns, like reduced public expenses. While social investments have been explored as political projects, the local practices of measurement they rely on remain scarcely studied. Based on a case study in Denmark, a social investment frontrunner, we first investigate how the idea of social investment was translated into a manifest model with repayment schemes seeking to quantify and make wellbeing commensurable with cost reductions. Building on observations and interviews with professionals in a social investment program for families in vulnerable positions, we then explore how they navigate inherent tensions of measurement. Contributing to the sociology of quantification, we outline three strategies used to handle such tensions: Measure modification to realign measurement with desired outcomes; Epistemic flexibility to enable the co-existence of diverging purposes of measurements; Temporal protraction to allow for time lag in measurement. The study illustrates how distinctions between conceptualization, measurement and use of numbers fade in practice when conventions are unsettled and practitioners assume an entrepreneurial ethos to make things work.