The Starcraft II Ladder and Possible MMR Decay

Are you having a more difficult time on the ladder lately? Don’t worry; you’re not getting worse as you probably think. The culprit may be the ladder itself with the possible introduction of MMR decay.

What exactly is MMR decay?

To put it simply, it’s the degradation of your hidden matchmaking rating (MMR) when you become inactive and stop playing. Prior to the latest season (Season 5), regardless of your activity, your MMR does not decay. This means that if players had a Masters MMR at the end of the season, they would stay Masters after they play their placement even if they only played one match the entire season.

Blizzard has always been very secretive about how the ladder system of Starcraft 2 works. Aside from league percentage and that there is a hidden MMR, Blizzard refuses to divulge information on how the system calculates ratings and promotions. This leads the community to figure out the system on its own. Lately, a tool to estimate the MMR of players have been created as a plugin for SC2 Gears called ‘MMR Stats’.

During the start of Season 5, players have reported demotions across the board. Masters players found themselves in Platinum, Diamond players in Gold, etc. MMR Stats users confirm the dip in MMR especially for players who have not played a few weeks before the start of the new season. Teamliquid.net user Excalibur_Z expands on this subject in his thread. Basically, it appears that Blizzard has introduced MMR decay.

What does this mean for the average ladder player?

If it does exist and is not an error in data collection, MMR decay could address a couple of things about the ladder. It keeps the ladder competitive and allows the system to accurately estimate a returning player’s skill level after a period of inactivity. This means no more losing streaks when coming back after a long break, assuming of course, that your skill level also diminished.

But what if it doesn’t? What if you were simply playing Unranked mode the whole time and not actually inactive? Therein lies the possible problem then. If inactive Masters players get demoted to Platinum due to MMR decay then I’d imagine legitimate Platinum players are going to have a bad time on the ladder.

Now a player or two who’s inaccurately demoted is not a big deal. But imagine a large percentage of Masters players get demoted to Platinum. True Platinum players will meet former Masters players a whole lot since their MMRs are suddenly evenly matched although their true skills are not. To top it off, former Masters players are possibly pit against other demoted Masters players thereby preventing them from being promoted since their skills would still be equally matched.

These situations are reflected by the percentages of league distribution in the global ladder. According to nios.kr, only around 6% of the player base are Diamond down from the 18% that it’s supposed to be. Platinum is down to 10% from the 20% it’s supposed to be. While this competitive ladder can be for the better in the long run, it is extremely frustrating and demotivating especially for lower leagued players who are trying to climb the ladder. Imagine doing your best to get out of Gold and into Platinum, only to be demoted and placed into Silver losing to Bronze players the next season.

While it is not sure whether MMR Decay is implemented or not, collected data and observations by the community points to the fact that Blizzard has implemented the decay at least for Season 5. Whether this could be a good thing or not remains to be seen.