Yep I showed as an au on my dads account since 2003 without a social, I believe that helped me get to where i am now.
I'm not sure why that would help. On every credit report that I have seen, Citi specifically states that this is an account of an "Authorized User." Lenders know, when they make an inquiry, what authorized user means - in other words, just because you're an AU, it doesn't mean your a credit worthy risk. After all, it's
someone else who is on the line, and it's that someone else, not you, who is presumably paying on time and consistently.