The Making Of Index Numbers; A Study Of Their Varieties, Tests, And Reliability. PREPATORY NOTE. All sciences are characterized by a close approach to exact measurement. How many of them could have made much progress without units of measurement, generally understood and accepted, it is difficult to imagine. In order to determine the prmsure of steam, we do not take a popular vote we consult a gauge. Concerning a patients temperature, we do not ask for anybodys opinion we read a thermometer. In economics, however, as in education, though the need for quantitative measurement is as great as in phyaics or in medicine, we have been guided h the past largely by opinions and guesses. In the future, we must substitute measurement for guesswork. Toward this end, we must all agree upon instruments of measurement.