Inter-League Adjustments

Teams from different leagues play against each other in European competitions and exchange Elo points. This means that leagues exchange Elo points as well. However, when one observes the leagues' Elo differences over time, it becomes clear that leagues do not exchange enough Elo points just by the few European matches each year. The Elo values will then be very inert and it takes decades for formerly weak leagues to catch up with formerly strong leagues.
So these ranking will apply an additional measure: Every time a club exchanges Elo points with a club from another league, on top of the exchanged points from the clubs, the leagues will exchange points as well. A certain amount of points will be added to the league's clubs, uniformly distributed. To find out how many points are ideal, I tested what factor is required to provide the best predictability for European Cup games. The following table shows how many points are exchanged per team and per league in a European Cup game:

Elo points factor: Team + LeagueNLOP1L2L
Team's league not covered2+02+02+02+0
Only national playoff matches covered1+1+11+11+4
One League from team's assossiation covered1+11+21+51+5
Two Leagues from team's assossiation covered1+11+51+51+11

A team that plays in a league that is not covered will gain or lose twice as many points as it would normally do to compensate for the effect that the team has very few games. Simliar if there are very few domestic matches from an era available, then the factor is 1. If a team plays regularly in a league then a European Cup game counts as a normal game for this team.
If a team does not play in a league, then there is no Inter-league adjustment. If a team plays regularly against national opposition, then the Elo points that one team wins or loses at international level are multiplied by 6 (minus the Elo points of the playing team itself) and uniformly added to the league's teams. If both team's assossiacions have two leagues this factor is doubled.
This leads to the unelegant consequence that a club can start a game with a different Elo value than its last post-game-value.
However, this method reacts quickly to new balances of power in European football. These Football Club Elo rankings do always want to represent the exact winning probabilities of a potential or actual encounter between two teams based entirely on results.

Created: 23 Mar 2013 - Modified: 22 May 2012