so the spirit of the Big Mac Index is the spirit of PPP. Yes. The Economist came up with the Big Mac index as something of a joke a few decades ago but it proved to be unreasonably effective. It also has a merit of being simple and pretty transparent.
It definitely is a valid question. However I feel different on estimates of "stuff" being produced in countries that don't have massive grey market economies. (Note unemployment is tricky and overly technical about whether people 'want' to be in the labor market -- this seems to be necessary but frequently gives the wrong impression unfortunately.)
Further, the bar charts have footnotes for sources. In particular, one of the two bar charts explicitly cites the "Bureau of Labour Statistics" for the 2006 GDP per hour worked numbers (which they cutely misspelled as British). I presume this page is what you'd want to comb through:
https://www.bls.gov/ilc/intl_gdp_capita_gdp_hour.htm#table01
per that BLS page
in general you wouldn't want include capital
earnings, just the amount of
stuff being
produced. (And yes 'production' includes services.)
By tradition, the private sector accounting for 'stuff' produced is allocated to L and K (as in Labor or Kapital) as a nod to Marx.
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I don't view
The Economist's reporting of data from BLS as being politics. And I do view BLS as being a pretty good data source.
Economics is not exactly on sound footing as a 'science' but I'm not suggesting predictive models or causation here -- just (economic)
accounting. And yes even the accounting is difficult but it is a considerably more modest goal than predictive modeling.
The other picture cites conference board:
https://www.conference-board.org/data/ and CERA. I have lingering concerns that CERA may be too political right now, though the chart and its data is a few years old.
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It may be that you're genuinely interested in the details underlying this data... there was a time when I was too. I've gone through
some of this in detail a while back -- I find it rather unpleasant these days. You're certainly welcome to go through those links (BLS in particular) but it may warp your brain.
Unfortunately in the real world I observe an overwhelming trend where people only ask detailed questions about data when it makes them feel uncomfortable (cognitive dissonance). It's this bit of pattern recognition that I picked up on -- fairly or not. No offense intended. Es tuet mir leid if any was caused.