This isn't talking about where US dollars are - it's comparing incomes. The numbers are in USD for convenience's sake, but you could easily convert them to euro

This isn't talking about where US dollars are - it's comparing incomes. The numbers are in USD for convenience's sake, but you could easily convert them to euros, rubles, yen, or krona if you wanted. Of the three lists on the page you linked, the smallest different is $8151, not $6k. You're right that the article doesn't account for purchasing power - they only do it for US states. Of course, that doesn't help your case since Sweden is a more expensive place to live than most of the US. I won't touch your point about the Spanish Empire because I assure you that I don't understand whatever it is you're trying to say well enough to discuss it.