Stadowstats uses proprietary calcs but it's easy enough to reverse engineer the numbers. I can share the spreadsheet if you want, but it boils down to nothing more than headline-CPI with a fudge factor --which is why the exact numbers are kept under wraps. Anyone doing serious work in the marketplace has to use transparent functions of actual purchase prices.
Shadowstats's target audience are the political enthusiasts with little knowledge of economics.
expat_panama,
Congratulations your have gone full circle. There is nothing wrong with using a ‘fudge factor’, if it is accurate.
And again you ignore the addressed nor denied the corruption of the CPI by using soft metrics such as hedonics or the substitution effect, both of which are wide open to manipulation by the latest power that be. Also ignored is the effect of shifting arithmetic weighting of the CPI components was to a geometric weighting which automatically gives a lower weighting to CPI components that are rising in price, and a higher weighting to those items dropping in price. Weighting works in conjunction with the substitution effect.