This edited volume contains various contributions from economists, historians, political scientists, sociologists and statisticians, all of whom share the same approach to quantities. Whether they be dealing with national, European or international statistics on the homeless, occupational health or economic governance, they all emphasise the extent to which the numbers are based on conventions and they all call into question their assumed obviousness by examining the exercises in quantification that produced them. To put it another way, they all explore the ‘black boxes’ constituted by the indicators, categories, scoreboards and other accounting or statistical tools that serve both as evidence and as instruments of government. This is the fundamental lesson to be drawn from the work of Alain Desrosières, statistician, historian and sociologist of statistics, whose work has inspired and guided a large number of studies since the end of the 1990s. The aim of this book is to give a general idea of the research that has its origins in the approach pioneered by this eminent thinker on large numbers and the politics underlying them.