That doesn’t exist.
Forced loss streaks
There is an old and persistent conspiracy theory that Blizzard’s algorithms force players to have a 50% win rate by nefarious means (if a player is doing well, very poor players are put on his team to make him lose, often for many games in a row). This has been contradicted by Blizzard7, 46, is contradicted by people’s ability to climb13, and would be a horrible and difficult-to-implement design. The truth is much simpler. If a player wins more than he loses, his SR/MMR goes up. As it rises, he is placed against stronger opponents (and with stronger allies), which increases the chance that he will lose7. Once in equilibrium, the average person he faces (and is allied with) is at his skill level, and the only way to go up is to become a better player. The win/loss patterns and streaks are fully consistent (in the mathematical sense) with the system as Blizzard describes it, and are not consistent with a system in which Blizzard forces wins and losses34.
Matchmaking takes into account win percentage
It explicitly does not. “At no point in MMR calculations do we look at your win/loss ratio and win/loss ratio is never used to determine who to match you with or against. We are not trying to drive your win/loss percentage toward a certain number” – Jeff Kaplan (32). However, probability of winning depends the difference between MMR and a player’s skill level, and MMR does depend on how much a player has won or lost lately, so in this way there is an indirect dependence of win probability on win/loss history. This leads to (correct) statements that “Whenever I reach, or am near, my career high, I start losing and fall back down”. This corresponds to a player reaching his skill cap. The only way to break out of an MMR/SR range is to improve as a player and play a sufficient number of games.
Oh, crap, sorry. It’s a real bummer when evidence ruin’s people’s good old conspiracy theories.