" price index "

[Noun]  | "price index" 

1: an index number expressing the level of a group of commodity prices relative to the level of the prices of the same commodities during an arbitrarily chosen base period and used to indicate changes in the level of prices from one period to another

Origin: 1886 ;

[Noun]  | "consumer price index" 

1: an index measuring the change in the cost of typical wage-earner purchases of goods and services expressed as a percentage of the cost of these same goods and services in some base period —called also cost-of-living index

Origin: 1945 ;

[Noun]  | "the retail price index" 

1: a list of prices of goods and services that shows how much prices have changed in a given period of time