Is it really? If you look past Western Europe and North America it is definitely not. And even there you can see things, like that spike in Bay Area. Except for population size, there seem to be at least two more major factors at play: wealth and English proficiency. Even in Europe they are clearly visible: Oslo and Sofia are about the same population, Rome is at least three times more populated than Edinburgh. So, no, not really.

+1

It does correlate quite a bit to city population, although, the spike in what I presume to be Austin, relative to Dallas or Houston is quite telling.

That was the biggest surprise to me. I know Houston has over twice as many people but I didn't expect the numbers to be that large of a difference.

i thought the same when looking at the US, but then I noticed Los Angeles. L.A. is the 2nd largest city in the US, and the smaller spike, compared to its population, is consistent with what I've heard about the tech scene there.