  Assessing the skill level of players to predict the outcome and to rank the
players in a longer series of games is of critical importance for tournament
play. Besides weaknesses, like an observed continuous inflation, through a
steadily increasing playing body, the ELO ranking system, named after its
creator Arpad Elo, has proven to be a reliable method for calculating the
relative skill levels of players in zero-sum games.
  The evaluation of player strength in trick-taking card games like Skat or
Bridge, however, is not obvious. Firstly, these are incomplete information
partially observable games with more than one player, where opponent strength
should influence the scoring as it does in existing ELO systems. Secondly, they
are game of both skill and chance, so that besides the playing strength the
outcome of a game also depends on the deal. Last but not least, there are
internationally established scoring systems, in which the players are used to
be evaluated, and to which ELO should align. Based on a tournament scoring
system, we propose a new ELO system for Skat to overcome these weaknesses.
