r/boardgames • u/The-Phantom-Blot • 5h ago
Question BGG Rankings Re-Factored using Standard Deviation and Raw Ratings
A recent post about trying to get the top-ranked game on BGG to a gaming group table reminded me of this dilemma. Many of the games on BGG have an unusual number of high ratings, and specifically ratings that are concentrated at one or two high numbers.
BGG tries to compensate for this using a "BGG Rating", which is called "bayesaverage" in the CSV export of the rankings (you must be logged in to download). Rumor has it An unsigned Wiki article says that this is done by adding a bunch of a variable and unknown number, but at least 500 neutral (mid-number) votes to balance out any unusual number of high or low votes. (See pic 3 - I put this last because it duplicates the rankings on BGG already.)
This seems kind of lacking to me. To figure out the effect of the BGG ranking, I re-factored the rankings using the raw average rating. (See pic 2.) Most games didn't move too much, but Frosthaven and Clank! Legacy moved up a lot. I think this is because these games had an unusual number of bad reviews in the 1-3 range. After reading through some of those bad reviews, some of that was because of Kickstarter fulfillment problems. Some was because of bad fit for the gamers. So maybe the BGG rankings do achieve some kind of normalization.
Another potential way to improve the ratings is by looking at the "Standard Deviation" of each game's ratings. BGG helpfully tracks this on the Stats page for each game, but unfortunately it is not included in the CSV download. Stats experts will know more than me about how this is calculated, but it basically evaluates the "curve" of numerical ratings against a "standard" curve. An unusual ratings curve gets a higher SD. A "normal" ratings curve gets a lower SD.
So, in an attempt to balance out the BGG rankings "for normies", I took the raw average rating and divided it by the SD. I only did this for the top 30 games because I had to type in the SDs manually and regenerate rankings, so I didn't want to spend excessive time on it. (See pic 1 - this is the lead pic to match the title.)
In this re-factored ranking scheme, games like LOTR: Duel, 7 Wonders Duel, Concordia, and Lost Ruins of Arnak shoot up the rankings. Games like Brass: Birmingham, Gloomhaven, Pandemic: Legacy and Twilight Imperium drop significantly.
What do you think of the re-factored rankings? I think it helps balance the rankings toward more crowd-pleasing games. I'm sure it's not perfect. All the data is still from within the realm of BGG users, which is a limitation. Any suggestions for improvement?