The Playmate Indicator

Interesting, but very questionable.

The argument seems to be rooted on evolutionary psychology: when times were tough in hunter-gatherer days, men needed women who could pitch in with work to help them survive. Plausible in general, but I'm skeptical of the exact definition used for "difficult social and economic conditions". In hunter-gatherer days, this meant droughts, blights, storms, epidemics, and other disasters that made you starve or freeze to death. In contrast, even in difficult economic times, modern middle-class American men (i.e. who could afford Playboy) probably do not have to deal with anything approaching the level of duress needed to make this survival instinct kick in.

By the way, not to be dismissive, but I think the term "cute-o-nomics" was invented for studies like this.