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+--- Thread: Issue with FM and side advantages (/showthread.php?tid=9549)
Issue with FM and side advantages - Canadice - 2026-05-10
During the past week, we have been investigating the S25 FM files across the major and minor leagues due to suspicions that there is an unintended effect of the Home/Away matchup, despite matches being played in neutral stadiums.
After rigorous testing we found evidence that the number of fans for each team has an inherent effect on the home win rates. (ISSUE 1)
After this we also identified another database setting error that caused the first matchday of MD11 - MD15 to NOT be played on a neutral venue. (ISSUE 2)
ISSUE 1
Background
When neutral stadiums were introduced in S18, the settings in the FM Editor were set in a way that the attendance during the matches was perfectly split 50/50%. As the FM Database editor is a conundrum and more of a black box, it was never determined exactly which settings led to this result. The effect was then attributed to the move to neutral stadiums as other "evidence" found online at the time said that attendance had no effect on the advantage.
At some point in re-creating the FM file in S22, some settings were changed which led to an uneven split of fans in attendance. This was never identified and investigated as the teams were still playing in neutral stadiums, so it was assumed that the same effect persisted.
With the creation of the S25 FM File some settings was once again changed (overall increase in attendance for games) and we started getting more and more reports of heavily skewed win rates (in testing) for the home team which led to this investigation.
During the testing, different settings for team attendance and season ticket holders were set using FMRTE and its effect on the same matchup were measured over 100+ samples each. We saw a drastic shift (~40 percentage points) in home win rates when the attendance was unevenly (favoring the home team) or evenly split.
Consequences
Between S22 and S24, the league has had an equal number of home games played so the effect of the "home field advantage" evened out over the season. With the addition of the third round in S25 this is no longer the case, hence we need to make a fix to even the field for MD11 - 15.
The post MD10 files will include an adjustment of the team's season ticket holders so that the attendance for each game is split 50/50 for the remainder of the season.
This will also be done in the Cup file for the upcoming Quarter Final matchday. We understand that this effect has been in play for the previous matchdays as well, but we will not issue a re-sim of the previous rounds. The cup is inherently more "random" with both a random draw and the one leg knockout. We've also seen historically less effects of the home field advantage in the Cup over the past three seasons than in the league games.
ISSUE 2
Background
When creating the new database for S25, we added a third round of matchups to increase the season length to 15 matchdays. For Majors Division 1, I missed setting a neutral venue for the first game of the new matchdays (MD11 - MD15), thereby making them real Home / Away matchups.
This causes more issues than issue 1 due to the nature of how FM looks at splitting attendance for Home / Away compared to Neutral venues. The same solution for Issue 1 does not fix Issue 2.
Consequences
As the matchups are grouped in sets of five matchdays, the solution in this case is, ONLY FOR MAJ DIVISION 1 to go back and re-use the MD1 - MD5 file and schedule to play the remaining five matchdays. With the neutral venues and the fixes to the attendance split this will be the same scenario as all other divisions.
The index will need manual adjustments after the season is completed to reflect the correct matchdays but it is doable. Just bear with us until a couple of days after the final matchday to get a proper finalized index for S25.
The promotion playoff can be scheduled correctly using FMRTE by changing the results of MD11 - MD15 of Major Division 1 to the real results recorded in the other file, so those index statistics will be recorded properly.
Because of these issues @Canadice forfeits their seasonal pay for database / fileworker and a checklist will be created and sent out to relevant members to go through and double check that all settings are correct whenever a new file is created.