Startled by "Newsweek"
 

FEMALE FANTASY
Sex researchers and psychologists are noticing an interesting trend among
women – many fantasize about being dominated, and even spanked, in the
bedroom. The bestseller “Fifty Shades of Grey,” is just the latest incarnation
of the submissive trend. These fantasies, say the experts, stem from the
new in-charge roles women play in the workplace and the fact that four in
ten women now outearn their husbands.

Source: Newsweek, 4/17/12

I guess I am just too old but it would be embarrassing to me if I had a wife that out earned me :)