[gaius]

Reddit, most likely HN too.

That would be stretching my personal definition of social media, but yes Reddit does publish figures showing it's pretty much exactly as skewed towards men as Instagram is towards women, very interesting. I wonder about Strava, there seems to be no data available on that, maybe because it isn't ad-supported.

The reason I'm not so sure as neither Reddit nor HN are oriented around the personal profile in the same way as the others are. HN could (probably should) go completely "anonymous coward" and it would be no less useful.

[pbhjpbhj]

How does Reddit know?

[Scriptor]

They use the marketing companies that use 3rd party cookies to track you on every site you visit.

[pbhjpbhj]

So it's "you self-reported you were [fe]male on some other site; you didn't block scripts; ergo you're [fe]male".

Actually this https://www.techjunkie.com/demographics-reddit/ lists a few sources. The primary one appears to be Pew Research, the methodology is interesting http://www.journalism.org/2016/02/25/reddit-methodology/.

They random dialled, then surveyed 6000 people, ~4500 agreed to be surveyed further (with cash incentive), of those ~300 are Reddit users and the stats are taken from there. You can choose to do the survey by web or regular mail .. respondents who agree to be surveyed by mail actually take the survey at a level of 20%; if I read correctly they assume none of those sent the mail survey are net users.

The point of the survey was analysing political activity.

It seems likely to give only broad indications at best. Unfortunately this result from < 300 USAmericans seems to be repeated as "this is the global demographic of Reddit" in a few places.