Deflator

In statistics, a deflator is a value that allows data to be measured over time in terms of some base period, usually through a price index, in order to distinguish between a changes in the money value of a gross national product (GNP) that come from a change in prices, and changes from a change in physical output. It is the measure of the price level for some quantity. A deflator serves as a price index in which the effects of inflation are nulled. It is the difference between real and nominal GDP.