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Chain-type Quantity Indexes

A quantity index is an index number that measures the change in the level of a quantity from a base year, apart from any changes in relative prices. The value of the quantity index is 100 for the base year.

BEA uses chain-type annual-weighted indexes, also known as Fisher indexes, as its measure of real output and prices. These measures allow for the effects of changes in relative prices and in the composition of output over time, thereby eliminating a major source of bias inherent in fixed-weight indexes.