See Bloomberg's Peter Orszag column on Chain CPI
Something I pointed out in my post which is that this really will have small and diminishing impact looking at the data last few years.
"What neither side seems to have noticed, however, is that the difference between the chained CPI and the standard CPI has been diminishing."
"Over the course of those 13 years, however, the differences between the annual growth rates of the indexes have become substantially smaller. From January 2000 to January 2003, the annual increase in the chained index was 47 basis points lower than that in the CPI-U. From 2003 to 2006, the difference was 31 basis points. From 2006 to 2009, it dropped to 15 basis points. And over the past two years, the average difference has been just 11 basis points."
"Why is this happening? Examining the subcomponents of each index, it appears that housing and other goods and services have played a role. Sorting through the causes is complex, however. In any case, the more relevant question is, what is the best time period to use as a historical basis for projecting future differences in the indexes?"