After tax is quite misleading if "tax" includes services that cost a fortune in some "low tax" countries. Now, how would that look like if the graph were, "after tax and after all pension and health related expenses"? Quite a bit different I would assume.

Want to see the cost of a big mac in those places.

Does that say 10,000? 10,000 per person per year? So 60 per day per person, clearly this doesn't price in supply and demand equilibrium.

Counting or not counting the monopoly pieces

Is this based on average income or median? I'm guessing it's average as wealth inequality is going to skew things higher.

In Japan, the median salary is ~3.5 million JPY pretax (~48% of people make between 3 and 4 million gross) and big cities are helping that a lot. It would be roughly 2.55m after tax (a bit north of $16k USD as of today). That's not buying a lot of big macs.

This is the Big Mac Index, created by The Economist, a UK publication.

It seeks to understand the practical exchange rate between countries based on a broadly available, relatable, common good, rather than foreign exchange markets. It’s US Dollar centric as is the global economy (although that is changing).

The postwar global cultural impact of USA army bases everywhere makes the prices of things like the Big Mac and Coca Cola uniquely comparable between countries.

that's fun because in France, half of the wage is socialize in order to have healthcare and not big mac. So the graphic is fallacious but accidentally based