Club ranking systems are built inside confederations, and each measures results in its own competitions. Comparing a club's ranking with one from another continent misreads what the number does.
A coefficient measures a closed system
Continental rankings accumulate points from matches within that confederation's competitions, so the pool of opponents is limited to clubs from the same region.
Within that pool the ordering is meaningful, because every club is being measured against roughly the same field over the same period.
Across pools the number has no shared reference. Two clubs with similar coefficients have beaten entirely different sets of opponents in entirely different competitions.
Competition structures differ enormously
The number of matches available, the balance between group and knockout rounds, and the number of qualifying stages all vary between confederations.
A system awarding points per match rewards clubs in competitions with more matches, independently of how strong those clubs are.
Weightings attempt to correct for this, and the corrections are judgments, so the comparison rests on someone's estimate rather than on measurement.
Travel is a competitive input, not a footnote
Some continental competitions require journeys of several thousand miles between group matches, across multiple time zones and climates.
Others are contested within a few hours' flying time, so squads play the same number of matches with a fraction of the physiological cost.
Rankings count results and not the conditions that produced them, so the harder route earns no credit for being harder.
Intercontinental fixtures are too rare to calibrate
The obvious solution is direct comparison, but clubs from different confederations meet only occasionally and usually in single matches.
A small sample of one-off games, played mid-season for one side and out of season for the other, is weak evidence about the relative strength of two competitions.
Expanded intercontinental club tournaments increase that sample, though they still involve too few matches to calibrate coefficients that count hundreds of results.
The rankings still do a real job
Their actual function is administrative: allocating entry places to national associations and determining seeding within each confederation's own draws.
For that purpose an internally consistent measure is exactly right, and comparability across continents is not required for it to work.
The confusion comes from reading an allocation tool as a global ranking, which is a use it was never designed to support.


