Over the years, the methodology used to calculate the CPI has also undergone numerous revisions. According to the BLS, the changes removed biases that caused the CPI to overstate the inflation rate. The new methodology takes into account changes in the quality of goods and substitution. Substitution, the change in purchases by consumers in response to price changes, changes the relative weighting of the goods in the basket. The overall result tends to be a lower CPI. However, critics view the methodological changes and the switch from a COGI to a COLI focus as a purposeful manipulation that allows the U.S. government to report a lower CPI.
John Williams, a U.S. economist, described his view of this manipulation when he was interviewed in early 2006. Williams prefers a CPI, or inflation measure, calculated using the original methodology based on a basket of goods having quantities and qualities fixed.
David Ranson, another U.S. economist, also questions the official CPI's viability as an indicator of inflation. Unlike Williams, Ranson doesn't espouse the viewpoint that the CPI is being manipulated. Instead, his view is that the CPI is a lagging indicator of inflation and is not a good indicator of current inflation. According to Ranson, increases in the price of commodities are a better indicator of current inflation because inflation initially affects commodity prices and it may take several years for this commodity inflation to work its way through an economy and be reflected in the CPI. Ransonâs preferred inflation measure is based on a commodity basket of precious metals.