i would say amex
I always assumed it was ALL?
Capital One, BOA, and Discover (among others) do report and do backdate the full credit history.
Amex doesn't report the backdated credit history.
My "depth of credit" is significantly above my age due to being an AU on one of my father's AmEx cards.
You used to be able to get an AU with older accounts and it would backdated your history to theirs. Doesn't anymore.
But I guess it only works if you were made an AU before they made this change:
Heard of the amex change. Was chase always that way? Any DPs?
Chase does not take the SS number of AU's. Chase will usually only report an authorized user if they can match up in their own system a relationship between the primary cardholder and the AU.