Etymologically, an indicator, like an index, has to do with pointing. Anatomically, the indicator muscle (extensor indicis) straightens the index finger. Logically, indicators detect, point or measure, but do not explain. An index in the social sciences typically combines or synthesises indicators, as with the ‘index of leading economic indicators’, which aims to maximize the predictive value of diverse measures whose movements anticipate the rise and decline of general economic activity. A quantitative index or indicator typically cannot measure the very thing of interest, but in its place something whose movements show a consistent relationship to that thing. Since its purpose is merely to indicate as a guide to action, ease of measurement is preferred to meaning or depth. The indicator ranks among the varieties of information whose ascent has been so steep within the intellectual economy of modern times, tending perhaps to crowd out those more exigent epistemic forms, knowledge and wisdom.

We might even be tempted to categorize the indicator as an administrative or behavioral technology rather than as a mode of scientific understanding. Given the scientific hopes that have been invested in the design of effective indicators and the outpouring of scientific writing that has been brought to bear on them, this would be cavalier. Also, while managerial effectiveness is clearly not least among the stakes in a world of indicators, they are also pursued to promote informed action and decisions of a decentralized sort. For example, the Bureau of Agricultural Economics in interwar United States made strenuous efforts to anticipate harvests as a basis for estimating prices so that widely-dispersed farmers would not be wholly at the mercy of the companies whose agents showed up with an offer for their corn or wheat. On many matters, however, the knowledge of local people at the scene of the action, such as the manager of a factory, may be superior to that of executives in the head office, many miles away. Here, the availability of a numerical indicator, defining perhaps a standard of performance, can compensate somewhat for their informational disadvantage. Or finally, an official number might provide a neutral basis for adjusting contracts to changing circumstances. Cost-of-living measures began to be used this way in labor negotiations in the United States after the First World War, and later were even made automatic in some union contracts as well as social security payments.