Index Number

 An index is a statistical measure of changes in a representative group of individual data points. These data may be derived from any number of sources, including company performance, prices, productivity, and employment. Economic indices track economic health from different perspectives. It is anumberindicatingchange in magnitude, as of price,wage,employment, or productionshifts,relative to themagnitude at a specifiedpointusuallytaken as 100.

 The primary role of index numbers is to simplify otherwise complicated comparisons. It is especially useful when comparing currencies that have lots of different nominal values. Some countries even use index numbers to modify public policy, such as adjusting government benefits for inflation.