Hier einige Feststellungen zum Elo-Rating:
Elo ratings are a comparative only, and are valid only within the rating pool in which they were calculated, rather than being an absolute measure of a player's strength.
Elo did not specify exactly how close two performances ought to be to result in a draw as opposed to a win or loss. Actually, there is a probability of a draw that is dependent on the performance differential, so this latter is more of a confidence interval than any deterministic frontier.
The Elo ratings of these various organizations are not always directly comparable, since Elo ratings measure the results within a closed pool of players rather than absolute skill.