1. AU accounts don't actually help the AU's credit, except that it assists with FICO
2. If a young person has no credit, then they don't have a FICO score. An AU account can help to establish a CR TL that allows a FICO to be generated.
3. The AU account is calculated (for FICO) in account "oldest" "average age" "total of credit limits" and thus "credit utilization."
Traditionally, an AU account demonstrated to potential creditors that the individual had exposure to credit through the authorized use of a family members account. This used to represent the "training" and "education" of the young person in the proper care and use of credit. And for this, creditors (and FICO) used this as a second tier consideration for the AU's credit.
Fast forward...as people began to understand how the AU accounts were being viewed by lenders...people began leveraging that in ways not originally intended by creditors and credit risk analysis companies (FICO, etc.). This is why FICO and others have considered discontinuing the practice of using AU's in score and credit consideration....
However, due to the out cry of those who do legitimately use AU's for the training, education and introduction of credit to family members, FICO reconsidered and determined they would continue to use AU but are going to devise methods to better determine "legitimate" AU accounts and those that are likely to be "shadow trade lines" used to inflate FICO and water down derogs.
IMO IME 