Fisher index

Quantity or price index for an aggregate that is computed as the geometric mean of the corresponding Laspeyres and Paasche quantity or price indexes for that aggregate. One characteristic of these indexes is that the Fisher quantity index for an aggregate multiplied by the Fisher price index for that aggregate equals the relative change in current-dollar expenditures—that is, the ratio of the expenditures of the current period to the expenditures of the previous period. In the NIPAs, percent changes in quantities and prices are computed from chain-type indexes that are calculated using a Fisher formula.