Changes in quantities and prices are calculated using a Fisher formula that incorporates weights from two adjacent time periods. Because the Fisher chain-weighting formula is the basis for the PCE chain-type quantity and price indexes, weights change every quarter and there are no fixed weights associated with their derivations. However, shares computed from current-dollar PCE expenditures approximate the relative-importance weights used to construct the percent changes for chain-type PCE quantity and price indexes for a given period. These expenditure values can be found in underlying NIPA table 2.4.5U. on BEA’s Web site. For more information on constructing chain-type price and quantity indexes, please see chapter 4 of the "NIPA Handbook: Concepts and Methods of the U.S. National Income and Product Accounts."
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