So I've been seeing a lot of discussions about how Valve created an algorithm that ensures everyone has a 50% winrate. I just wanted to confirm that this is true:
What Valve has done is assign a number to everyone's account that goes up when you win, and goes down when you lose. They then use this number during matchmaking to make teams with a roughly equivalent sum of their numbers. If you are a better player than the average player with the same number, you naturally win more games than you lose, but this leads to the insidious part – winning more games makes your number go up, and the average skill among players with higher numbers is higher. Eventually, you reach a point where your skill is about equal to players with the same number as you, and your chance to win any specific game approaches 50%.
Naturally, there's a lot of factors at play in any single game, so the algorithm can't make you win a game following every loss. Sometimes you get lucky and win a bunch of games in a row. Now your number's really high, so you're less skilled than your similarly-rated compatriots, and your odds of winning each game drops. This can lead to losing multiple games in a row until your number goes down to where your skill level is.