I know https://publisherweekly.org/ shares stats like this from time to time. Source: about 3 years ago

See https://subredditstats.com/ (Comments per day, Posts per day). - Source: Hacker News / 6 months ago

However, using subredditstats.com we can get a few insights into how the year has gone. It just won't look as pretty. Source: 6 months ago

The end result was a stalemate. Reddit did not change any of its policies. Enough of the people responsible for posting and managing content left the platform. Here's a fun thing to look at, https://subredditstats.com/ for any major subreddit, e.g.: https://subredditstats.com/r/worldnews https://subredditstats.com/r/explainlikeimfive https://subredditstats.com/r/videos All of the most popular subreddits show a... - Source: Hacker News / 6 months ago

Reddit is the other place where huge political slap fights happened for America and a few others with massive legions of bots flooding the site with Qanon and Pizzagate making debuts here from 4chan, now its in a weaker position to fight bots than before and helmed by a man who thinks conspiracies are good. Posts and content uploads have slowed to a crawl, with what I see as a rapid rise of bot comments and posts.... Source: 8 months ago

So there is this website called subredditstats.com. You enter a subreddit's name and it lists a bunch of subreddits along with the percentage of user overlap with the entered subreddit. Ranging from 100% to 1%. - Source: dev.to / 10 months ago