Arena mode is a disgrace

[dschingis27]

Once a year I have to rant about it.

Arena mode is a disgrace for all players who try to have a serious competition. The fact that the Arena score is so sensitive for recent games is the most nonsense in all of BGA. You can't have the same sensitivity for Can't Stop, Harmonies, and Through the Ages. You have to adjust the K factor.
You are making this such a frustrating experience.

It's so blatantly obvious what BGA could do about it. Adjust the damn K factor for different games.
Currently for 2p games, the games that matter are about the latest 50 games you play with strong weight for the latest 20, 10, 5 games. This is utter nonsense for all games that have a significant luck factor which are sooo many games.

I am convinced that people play Arena despite the current system and not because of it. People crave competition and that's why they play but it could be so much more healthy and meaningful.

It's just so sad that we are still in this state in 2025.

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EDIT: The explanation of what I mean should not be hiding in a post at the end of page 2. So I copy/paste it here:

Here are some plots that prove my point (and illustrate what was nicely explained by euklid314).

These are based on a simulation. I compare two players, one starts with Arena score 1700, the other with 1800. (It doesn't matter where exactly I set the scores, what matters is that the difference is 100 at the beginning.) I simulate 100 games of these players against random opponents with Arena scores in 1500 to 2000. In the simulation, both players play the exact same sequence of opponents and get the exact same sequence of match results.

The plots show the Arena score difference between the two players after X games. It shows how quickly the original Elo difference is "forgotton". At the beginning, the difference is 100. With each equal match result, both Arena scores converge closer together, the difference gets smaller.

K=40 (current Arena system) https://imgur.com/a/CRxDagJ
K=20 (current Elo system) https://imgur.com/a/elo-difference-y-ax ... 20-Kxcf2ke
K=10 https://imgur.com/a/elo-difference-y-ax ... 10-Sz8DiwA
K=5 https://imgur.com/a/cRe1nWg

In general, this is expected/wanted behavior. If two players get the exact same results against the exact same opponents, then their Elo/Arena score should converge to the exact same value. The problem is how quickly this occurs. With a high K factor, the convergence is super quick and the original Arena score difference of 100 is nullified quickly. As pointed out, this is stupid for games with a strong luck component.

With K=40, the original Arena score difference of 100 is reduced by half already after only about 15 games. After 30 games, the difference is only at 20, meaning that 80% of historic performance difference is already forgotten after 30 games. (Note that it doesn't matter much what initial Elo difference I start the simulation with. Had I set a difference of 200 in the beginning, still about 50% of this difference is gone after 15 games, about 80% of the difference is gone after 30 games.)
There you have it, with the current Arena system, your score is mostly dependent on your last ~30 games, with stronger weight for the more recent games.

With K=20, it looks already much more reasonable, but the convergence is still way too quick for luck-heavy games. If there is a lot of luck, you need a longer series of games actually matter for the Elo/Arena score to get a somewhat meaningful performance score.

K=10 is something I could live with for games like 7Wonders, Railroad Ink, Harmonies. For games like Can't Stop or Lucky Numbers, you could even choose K=5. The effect is that less recent games are not downgraded as quickly for the Elo/Arena score, less sensitivity on the latest result.

Of note: This is for 2p games. Higher player counts are more complicated.
If you are interested in (not the best) R code that does the simulations, feel free to reach out to me.

[FrankJones]

I had no idea the K-factor is higher for different arena games based on .... ? I am not sure I entirely understood your post. Is this all explained somewhere on the BGA site?

[nik592]

I think the issue (for OP) is that the K-factor is the same across all games. OP thinks different games should have different K-factor, depending on luck vs. strategy for a given game, I guess? Currently, K-factor is only varied based on the number of games you have played - something like it's much higher for your first 20 games so you get to your approximately true ELO more quickly.

[FrankJones]

I think the issue (for OP) is that the K-factor is the same across all games. OP thinks different games should have different K-factor, depending on luck vs. strategy for a given game, I guess? Currently, K-factor is only varied based on the number of games you have played - something like it's much higher for your first 20 games so you get to your approximately true ELO more quickly.

Oh. Yes, that's (I think?) relatively common knowledge.

I am not sure I understand the OP's case for making some games have a higher or lower k-factor based on the luck element.
So, what exactly is the "disgraceful" part? Arena is a disgrace because all arena games have a K-factor of 20? That seems a bit hyperbolic.

[Jellby]

Arena is what it is. Play it if you want, don't play it if you don't. You can create/join other tournaments or play regular games outside Arena.

[euklid314]

EAS (Arena Elo) starts at 1500 and has a constant K-factor of 40.
For luck based games this produces swings of 100+ AES within 3-5 games (because you can win/lose against opponents of any strength). The current AES is a function of the last few game results.

In luck based games experienced players will have higher win probabilities. They might win 70% of their games. But in order to excel in Arena you just need a longer lucky win streak and then you must stop playing. AES is a very bad measure of playing strength. A lower K-factor would help because it would decrease those big swing and earlier games would influence AES more - not only the last 10 games...

That being said, I have already taken Jellbys advice and accepted the way it is.
In Backgammon I can reach top20 quite easily. Then I can decide to play on and reach top5 or fall back to top500 in the next 10 games or I stop at my top20 spot.
Position 1, 20, or 200 may be the result of the same Arena season with same win percentages.

[FrankJones]

EAS (Arena Elo) starts at 1500 and has a constant K-factor of 40.
For luck based games this produces swings of 100+ AES within 3-5 games (because you can win/lose against opponents of any strength). The current AES is a function of the last few game results.

In luck based games experienced players will have higher win probabilities. They might win 70% of their games. But in order to excel in Arena you just need a longer lucky win streak and then you must stop playing. AES is a very bad measure of playing strength. A lower K-factor would help because it would decrease those big swing and earlier games would influence AES more - not only the last 10 games...

That being said, I have already taken Jellbys advice and accepted the way it is.
In Backgammon I can reach top20 quite easily. Then I can decide to play on and reach top5 or fall back to top500 in the next 10 games or I stop at my top20 spot.
Position 1, 20, or 200 may be the result of the same Arena season with same win percentages.

This all makes sense to me.

There is a game here that I am confident I am the best at - but, it is an insanely high-variance game. The game is one of high skill in the long run - which would be thousands of hands - but in the short run, almost anything can happen. Because most people play the game in matches of 6 hands (which is a complete joke), there is almost no time for the skilled player's better plays to win out over short-term luck.

It is almost impossible to achieve 300 Elo at this game within these parameters, even though in the long run, skilled players will win thousands of points against weaker players.

Because of this, it's especially brutal to play Arena, where I will get randomly matched with players in the 100-200 Elo range against whom I have barely better than a 50-50 chance of winning such a ridiculously short match, which ruins my Elo very quickly.

So, I just don't play this game in the Arena.

[Romain672]

Hop: https://boardgamearena.com/forum/viewtopic.php?p=186571

[yodamus]

Join tournaments. Fill your competitive juices that way. Less of those elo complaints. Less of matchmaking complaints. Altogether a much better experience . Join. Have fun

[Ceaseless]

The game is one of high skill in the long run - which would be thousands of hands - but in the short run, almost anything can happen. Because most people play the game in matches of 6 hands (which is a complete joke), there is almost no time for the skilled player's better plays to win out over short-term luck.

Well, to be fair, a few thousand does seem a bit high for Arena.