[2023] After 13+ Years of the game being out, "Champions mained a lot have higher WR" has been officially debunked by Riot.

We know that players continue to not change their defensive shards against karthus Bot and that inflates the WR at least some amount relative to their true power level (and similar to a bunch of other mages bot).

Some of this is due to how hard it is to figure out where opponents are going in champ select, some autopilot and some ignorance.

It's worth noting that different champs have different "Mains Game Share" at different MMR's.

I tried many different interpretations of mains (MMR + Played over X games of champ, MMR + games played at Z rating, MMR + Y champ mastery, MMR + Games with a decay function for when the games were played), etc.

The most consistent one was just champion mastery at 100k+ (which helped, because it was also simpler to implement).

At 100k (compared to something like 50k) players were consistently outperforming 50k players, but hit a plateau of performance, so that's where I put the bar of performance increase for "being a main". It was also a relatively consistent static increase whether Masters+ players were considered or Silver players were considered.

The TLDR of this is mainly that:

• Newer players of the champion tank the winrate about as much as the mains increase it (lower quantity of mains, even if they are performing better relative to the observed WR than the new players are tanking it), with Katarina, Akali, Zoe being the most positive of the mains (and the rest of the champs, being close to 0% increase and in some cases negative)
• Newer players make up ~50% of the champ's plays on a given patch
• Moderate play makes up about ~30% of the champ's plays

It's about the same. the NET EFFECT is 0.4%, which is (high mastery effect on the observed winrate) minus (low mastery effect on the observed winrate).

High mastery players still perform significantly higher (~2% than the observed WR) for most cases