Consumer Price Index

Note on a New, Supplemental Index of Consumer Price Change

The Bureau of Labor Statistics began publishing a consumer price index (CPI) called the Chained Consumer Price Index for All Urban Consumers, effective with release of July data on August 16, 2002. Designated the C-CPI-U, the index supplements the existing indexes already produced by the BLS: the CPI for All Urban Consumers (CPI-U) and the CPI for Urban Wage Earners and Clerical Workers (CPI-W).

The C-CPI-U employs a Tornqvist formula and utilize expenditure data in adjacent time periods in order to reflect the effect of any substitution that consumers make across item categories in response to changes in relative prices. The new measure, said to be a "superlative" index, is designed to be a closer approximation to a "cost-of- living" index than the present measures. The use of expenditure data for both a base period and the current period in order to average price change across item categories distinguishes the C-CPI-U from the existing CPI measures, which use only a single expenditure base period to compute the price change over time. In 1999, the BLS introduced a geometric mean estimator for averaging prices within most of the index’s item categories in order to approximate the effect of consumers’ responses to changes in relative prices within these item categories. The geometric mean estimator is used in the C-CPI-U in the same item categories in which it is now used in the CPI-U and CPI-W. (See Monthly Labor Review, October 1998, pp. 3-7.)

Expenditure data required for the calculation of the C-CPI-U are available only with a time lag. Thus, the C-CPI-U is being issued first in preliminary form using the latest available expenditure data at that time and will be subject to two subsequent revisions. Accordingly, at the time of its introduction in August, "final" values of the C-CPI-U have been issued for the 12 months of 2000, "interim" values have been issued for the 12 months of 2001, and "initial" values have been issued for January-July of 2002. In February 2003, with release of the January 2003 index, revised interim indexes for the 12 months of 2002 will be published, and the index values for 2001 will be revised and will become final. Then, in February 2004, when the monthly expenditure data from calendar year 2002 become available, C-CPI-U indexes for the 12 months of 2002 will be issued in final form and values for the 12 months of 2003 will be revised and issued as interim. The C-CPI-U index revisions are expected to be small, but in principle each monthly index could be revised from its previously published level.

BLS previously has calculated superlative indexes on an experimental basis, although these are not comparable to the C-CPI-U in all computational details. (See, for example, Monthly Labor Review, December 1993, pp. 25-33.)

The C-CPI-U is issued for national averages only and will not be seasonally adjusted. It employs a December 1999=100 reference base. Data for periods prior to December 1999 have not been calculated. The component series that are published are listed below:

All items
Food and beverages
Food
Food at home
Food away from home
Alcoholic beverages
Housing
Shelter
Fuels and utilities
Household furnishings and operations
Apparel
Transportation
Private transportation
Public transportation
Medical care
Medical care commodities
Medical care services
Recreation
Education and communication
Education
Communication
Other goods and services
Services
Commodities
Durables
Nondurables
All items less food and energy
Energy

These indexes are published monthly in the CPI news release and the CPI Detailed Report, and the series is available electronically at the same site as other CPI data: http://www.bls.gov/cpi/.

For more information on the C-CPI-U, write to:

Bureau of Labor Statistics
Division of Consumer Prices and Price Indexes
2 Massachusetts Ave. NE, Room 3130
Washington, DC 20212

Or contact Rob Cage either by telephone at (202) 691-6952 or by electronic mail at Cage.Rob@bls.gov .

Last Modified Date: April 26, 2011

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