The objective of this article is to analyze the practices and challenges underlying the development and use of sustainability performance indicators in public organizations. Based on interviews with sustainability managers and experts (n = 39), analysis of strategic documents (n = 135), and participant observation within several organizations, the study shows that the governance-by-numbers system put in place by the government is largely dissociated from sustainability issues and real performance. The focus on quantifying performance and the verification mechanisms put in place do not lead to more rationality, rigor, or monitoring, but rather to a proliferation of unsubstantial information that paints a fictional picture of sustainability performance. Through the lens of the moral fictionalism approach, this study highlights the challenges of measuring sustainability performance and the reasons behind the production of quantitative data of questionable usefulness by public organizations. The study contributes to the critical literature on sustainability performance measurement practices, on the sociology of quantification, and on the fictionalist approach of governance by numbers.
