Too Young? Too Old? (Relationships and Age Differences)

An article written by an astrologer regarding the correlation between age and a relationship... He said the foolproof method of determining whether or not the age gap is appropriate lies in simple math:

"Cut the older partner's age in half....then add 7. If the younger one is younger than that...they're 'too young'. It doesn't matter how old you are, the same rule applies. If you're 30, you shouldn't go out with anyone younger than 22 (15+7). If you're 42, your partner ought to be at least 28."

This sounded pretty genius to me, so I thought I'd share.

Do you agree with the method? According to his formula, what's the youngest age you should date?

(My limits for being a 20 year old female are 17-26 year old men according to this)