> The average hours worked in France is 1500, UK 1600 and USA 1800[1]. Therefore if you factor in hours worked, a developer in France should be paid 83% of average salary in America and 94% of average salary in the United Kingdom. This of course assumes that everything else is equal (which is untrue).

Notably, the longer hours worked in the US compared to Europe comes at the expense of less per-hour productivity in most studies I've seen, though not enough to result in less per-worker productivity. If that's true within Europe as well, the value of the time worked would be closer than the number of hours would suggest.