Price index reference base.

Effective with publication of January 1988 data, many important PPI series (including stage-of-processing groupings and most commodity groups and individual items) were placed on a new reference base, 1982 = 100. From 1971 through 1087, the standard reference base for most PPI series was 1967 =

100. Except for rounding differences, the shift to the new reference base did not alter any previously published percent changes for affected PPI series. (See "Calculating Index Changes," below.) The 1982 reference base is not used for commodity indexes with a base later than December 1981 or for industry net output indexes and their products.

For further information on the underlying concepts and methodology of the Producer Price Index, see chapter 14, "Producer Prices," in BLS Handbook of methods (April 1997), Bulletin 2490. This document can be downloaded flom the BLS Web site at www.bls.gov/opub/honi/homch14_itc.htnl. Reprints are available on request.