I'm shoked by Lichess ratings. The graph indicates that 1380 Elo ranks you above 36% of Rapid players. On chess.com, 1200 Elo ranks you above 80% of Rapid players.
Just anecdotally, I’m an ~1800 rated player on chess.com, and ~2050 on Lichess. Percentile rank wise, I’m in the top 3.5% on chess.com, and closer to top 10% on Lichess.
I think this matches the general perception that Chess.com has many more casual players. This is likely a function of all the cross promotion they’ve done to grow the game, especially on Twitch. Neither site is “good” or “bad”, but my friends who play casually seem more likely to play on Chess.com.
> I’m in the top 3.5% on chess.com, and closer to top 10% on Lichess
You are correct that ratings are not comparable, but percentiles are not really comparable either. IIRC, chess.com computes the percentile rank on the overall player population, while lichess only compares the score of players who have been active in the last 7 days.
> Just anecdotally, I’m an ~1800 rated player on chess.com, and ~2050 on Lichess
I have similar ratings to yours on both sites, can confirm the anecdata.
> I think this matches the general perception that Chess.com has many more casual players.
I guess it depends on what you define as "casual". Chess is a game where ratings work beautifully because it's individual and there's not a lot of randomness, so your rating will converge on your skill in short order.
What I noticed is that there are a lot of casual players on both sites, but Chess.com has a "wider" distribution if that makes sense, with lots of absolute beginners (think <1100 chess.com), while lichess seems to have less of those.
Also, IIRC lichess has an absolute rating floor at 800, while chess.com doesn't have one.
Absolute Elo ratings have no meaning. The system is set up so that differences between Elo ratings are predictive of the outcome of a game. There's nothing anchoring the overall scale, though, and you can add in an arbitrary constant to every player's Elo without changing any of the predictions about who will win a given game.