What does my mmr mean dota 2

A collection of thoughts and problems

In Part 1, we discussed the potential for inflation/deflation in Dota 2’s ranked matchmaking system. In part 2, we will discuss some other effects and weaknesses of such a system.

Before we really begin talking about inflation at the highest level of play, we need to look at what it really means for a player to have a MMR of 4.4k.

The most comprehensive analysis of what it really means to have a certain MMR comes from this reddit post. By calculating the differences in total team MMRs, he/she could derive a relationship between what Valve’s matchmaking system thought the win chance was and how it related to the difference in MMRs. This graph is the end result. Simply put, 1k MMR points would roughly translate to an increase in win rate of about 25% at the same level.

However, there are several problems with this system.

Firstly, it is currently unknown to us as to whether this ratio changes from patch to patch. If it does not, MMR inflation would be a problem. Certain patches are more stable than others, in the sense that the better team is more likely to win. Take the current patch 6.82c as an example. With the new comeback mechanic in place, teams that make mistakes are more heavily punished, so the better team is usually more likely to come out as the winner. It is difficult to produce real evidence (perhaps through some analysis of dota2lounge statistics this may be possible, but I lack the skills to complete this process), but 6.81 was a far more chaotic patch as compared to 6.82c, and underdogs were more likely to win, probably as a result of the lack of this new comeback mechanic. If we take this to be true, what it means is that a 200 point MMR difference would now translate to an increase in win rate of greater than 25%. This means that while you obtain 10 points, which would translate to an expected 80% win rate, you are actually having an expected 85% or maybe even 90% win rate. This change in patch has resulted in a scenario where higher MMR players are actually favored more naturally. As higher ranked players are rare, Valve’s matchmaking system often places them in games where the MMRs are skewed, oftentimes with their teams having the higher MMR, favouring them in this new, more stable patch. This allows for the higher ranked MMR players to climb even higher and contributes to inflation at the highest level of play.

This brings to mind another problem with the current MMR system. The current MMR system attempts to match individuals with close MMRs with each other, so most games are completely even with little variance. This completely breaks the MMR system and renders the expected win rates meaningless. If players are not constantly exposed to a situtation where there is a large difference in skill between the two teams, this 80% win rate nets you 10 points effect is irrelevant. If games with 1k skill difference are rare (they currently are), then the fact that valve assigns the winning team only 10 points almost never comes in play, so the relationship between the scaling of points and the win rate is not controlled by Valve, but by the distribution of player skill. This means that the previous work done by /u/Zenotha on reddit is meaningless as that merely demonstrates what Valve thinks a 1k MMR difference means and not what it actually corresponds to.

Of course, Valve could have already implemented varying constants that change patch by patch or month by month that negate all of my concerns.

An interesting thing to note is that the current MMR system where players are matched with players with equal MMR, avoiding games with huge variance has possibly interesting implications. Imagine a scenario where a bunch of players of perfectly equal skill are dumped in a separate pool for matchmaking using Valve’s current matchmaking. Say we give them all an initial matchmaking rank of 4k. As the teams are perfectly even as all the players are even, it can be expected that the winners are all random. This means that as more games are played, due to the natural amount of variance, it can be expected that these players would all shift to a increasingly wider range of MMRs despite having equal skill. There is no equilibrating force in this case as there are no games played where the teams have large differing MMR points, disallowing players far from the mean to take advantage of their obscenely low/high MMRs to get back to the mean. In reality however, a equilibrating force exists in the direct relationship between MMR and player skill.

In the end, higher players increasing their MMRs over time was probably just a slow stabilization process as the higher MMR slowly adjusted to their real values.