a quantity whose variation over a period of time measures the change in some phenomenon.
Origin of index number
First recorded in 1870–75
Also called index.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
statistics a statistic indicating the relative change occurring in each successive period of time in the price, volume, or value of a commodity or in a general economic variable, such as the price level, national income, or gross output, with reference to a previous base period conventionally given the number 100
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012