Based on my own lived bias and HN addiction... The leading demographic has to be West Coast of the USA, then the multinational PNW as the most active HN users.

Again, I am biased, but as far as HN bias goes, that ain't bad. These are amazing places chock-full of the coolest people.

After decades of the West Coast life I now live in rest of world, and wish that rest of world could be so lucky.