The first leaders of the economics and sociology of conventions (EC/SC) forged the common heritage from a dual position of researcher and practitioner of official statistics. By putting forward the idea of measurement convention very early on, these economists insisted on the dual quality of conventions: both as a coordination device (allowing agents to act thanks to this uncertainty-reducing operator) and as a collective cognitive device in that official statistics operate as a framework for representing and interpreting the social, demographic, ecological, or economic realities that they make visible. This chapter builds on this common heritage to account for the richness of the work of measurement conventions, by circumscribing, in this applicative chapter, quantification to macroeconomic measures: inflation, gross domestic product (GDP), and growth. It is because some of these measures are in “crisis,” in the sense that they are less widely shared, and they are marked by a form of cognitive dissonance, and that work has multiplied in recent years, taking advantage of these crises to reopen the black boxes of measurement. Measurement conventions operate as discrete institutions, silent modalities of representation, and coordination that emerge through these dissonances.