A number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time. Synonyms:index, indicant, indicator.
... recently the prices of many commodities—among them rice and raw silk especially—have been coming down and this downward movement is gradually extending to all other commodities. From these considerations I deduce that the index number of general commodities may be safely taken as 200 when your book appears. The reader of your book has simply to double the figures given by you—that is the figures of 1915 and 1916—in order to get a rough estimate ... — The Foundations of Japan • J.W. Robertson Scott
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