June 21, 1999
Using current methods of calculation, the Consumer Price Index for All Urban Consumers (CPI-U) would have grown more slowly in the past 20 years. The average rate of inflation based on a new research series was about half a percentage point lower than the official rate in 1978-98.
In a new BLS study, the CPI-U was re-computed for 1978-98 using the latest methods. The resulting research series, dubbed the CPI-U-RS, rose by 4.28 percent per year on average over that period, compared with 4.73 percent for the CPI-U. As shown in the chart, in every year except 1982, the CPI-U increased by more than the research series.
BLS has made numerous improvements to the CPI over the years, which have increased the accuracy of the index; however, the official historical price indexes are not adjusted to reflect the improvements. The research series attempts to answer the question: "What would have been the measured rate of inflation from 1978 forward had the methods currently used in calculating the CPI-U been in use since 1978?"
CPI data are produced by the BLS Consumer Price Index program. It is important to note that the CPI-U-RS has certain limitations and that it is subject to revision. More information on the CPI-U-RS can be found in "CPI research series using current methods, 1978-98," by Kenneth J. Stewart and Stephen B. Reed, Monthly Labor Review preprint, June 1999. Annual percent changes are December-to-December changes.