Originally Posted by Necronaut
It's based on the skill level of your opponents. In other words if you beat two teams and get 4 points for each, the system knew you were way more skilled. If you lose to a team and lose 20 points, the system thinks you were more skilled and your opponent the underdog. This is why you can win more games for less value and lose fewer games for more value and end up demoted.
It's actually the exact opposite, as counter intuitive as that sounds. If you gain 3 LP, you were actually slated to lose
. The system believes you're not "worthy", as it were, of being where you are, so it makes it difficult for you to increase. Similarly, it makes it easier for you to drop.
However, your unviewable MMR (the equivalent of Elo) will go up more quickly in the games you gain a small amount of LP. As this gets closer to where you should be (and it will climb quickly if you continue winning these games), your LP gain will increase again.