At the AEA session on measuring well-being, Austan Goolsbee and Pete Klenow write in an abstract,
We use transactions-level data from Adobe Analytics to analyze inflation online vs. offline. Online inflation from 2014-2017 period averaged about 100 basis points lower than inflation in the CPI for the same categories. Entry and exit of new product varieties is extremely important in most online categories (but less so in food and grocery). Data on quantities is particularly important because the entry and exit rates vary with product sales. The increased variety of products sold online implies an additional 100 basis points of lower inflation than in the matched model/CPI style indices.
In my view “the” inflation rate is an increasingly dubious concept. People can argue forever about whether true inflation is really much lower or much higher than what the CPI indicates.
Because we do not know the true inflation rate, we do not know the true real interest rate or the true growth rate of real wages. Not to mention the fact that there is no such thing as “the” wage rate, given the divergence in wage behavior across different categories of workers.