The demographic trends in the GP aren't unique to America. They're more or less the rule in most developed countries, and I think it's safe to say most HN users probably come from developed countries.

Can you cite a source for that? How can you infer the demographics of HN in the absence of data?

Where I come from, it's pretty poor form to ask people to cite sources for obvious statements, without any other insight or commentary. After all, you're asking them to do work for you, but not taking basic steps to suggest you might appreciate their effort.

The preferred option is to do a little reading of your own beforehand, and to share whatever it is you know that makes you think the obvious answer might not be right.

Non American HN member here. It will apply here too. Me and most other people from Europe / Asia I know that are on HN are from big cities.

OP said "most[ly]" not "only". Just wanted to point out that your comment shifts the goal posts.

I disagree, we do not know the demographics of HN and the only sources cited deal with America specifically. It’s all speculation.