The Experimental CPI Using Geometric Means

On April 10, 1997, the Bureau of Labor Statistics introduced an experimental Consumer Price Index (CPI) for All Urban Consumers, using a geometric mean formula to combine individual price quotations at the lower level of aggregation while keeping the current Laspeyres arithmetic mean formula for higher level aggregation. This experimental index, called the experimental CPI using geometric means, or CPI-U-XG, is a supplement to the price information available from BLS and does not replace the published CPI-U or CPI-W indexes.

Table 1 shows the CPI-U-XG indexes for major CPI categories for the period from December 1990 through the latest available month.  The data are not seasonally adjusted.

Historical differences between the CPI-U and CPI-U-XG arise not only because of the different formulas used, but also because of methodological changes made in the CPI-U since 1990 that are reflected in the CPI-U-XG for the entire series. For historical comparison to the CPI-U-XG, therefore, BLS also has issued an experimental Test Laspeyres series called the CPI-U-XL, which differs from the CPI-U-XG only in the use of the Laspeyres formula for aggregation of price quotations. Table 2 shows the CPI-U-XL indexes from December 1990 through December 1997. The CPI-U-XL was discontinued after 1997.

These data will be updated and released monthly one week after release of the CPI-U. They are expected to be available on the Internet at at approximately 8:30 a.m. on the morning of their release.


Last Modified Date: October 16, 2001