Why statistics tend not only to describe the world but to change it

Lorraine Daston

• The Politics of Large Numbers: A History of Statistical Reasoning by Alain Desrosières, translated by Camille Naish
  Harvard, 368 pp, £27.95, October 1998, ISBN 0 674 68932 1

Is the Gross Domestic Product real? How about the unemployment rate? Or the population of the United Kingdom? These are entities that hover between the realms of the invented and the discovered. On the one hand, they are creatures of classification and calculation, of conventions of coding, modelling and sampling. It is the artifice of definition that makes them cohere – or unravel. Depending on the method by which GDP is reckoned (e.g. sum total of all rents, wages, profits, interest and dividends as against national expenditure on goods and services), or how unemployment is defined (without a job? without a job and actively seeking one?), different numbers result. More disturbingly for common-sense realism, these entities come into being (and sometimes pass away) in specific historical circumstances that don’t satisfy the usual criteria of solidity and permanence for bona fide things in the world. Why did the category of ‘unemployment’ supersede that of ‘poverty’ around the turn of this century? And why are international population and medical statistics so hard to standardise? On the other hand, statistical entities are robust and vigorous: GDP and the unemployment rate guide government planning and affect the outcome of elections. Actuarial statistics, which correlate the risk of car accidents primarily with horsepower in Germany but with the age and sex of the driver in the United States, set the price of policies and are the foundation of vast fortunes for insurance companies. The categories of national labour statistics are only approximately translatable, even among the homogenised economies of the European Community: to be a Beamter or cadre or manager is not just to assume a label, but to take on a distinct persona. If they are not part of the durable furniture of the world, the same everywhere and always, statistical entities nonetheless change the world. They are, as Alain Desrosières puts it, ‘things that hold’.