Even romance follows the laws of supply and demand:
Griskevicius and company then asked the test participants to indicate how much they would spend on three romantic gestures: a Valentine's Day gift, a dinner date, and the purchase of an engagement ring. When test participants believed men outnumbered women in the population, they expected men to spend more money on the items. This was true of both male and female participants — suggesting that when men have more competition for mates, women become choosier and men attempt to out-spend any rivals.Read the whole thing.
The research has its limitations. For starters, financial and mating decisions are complicated processes whose outcomes are hard to reduce to any single factor. Beyond that, it seems reasonable to wonder whether most people even know the sex ratio of their cities — and you'd have to know that ratio to act on it. Timing also seems important here: sex ratios might cause men to spend more during courtship, but what about once they start a family? There's a lot more to consider.
Still the theory is incredibly intriguing. In the latest issue of Current Biology, British researchers Aron Szekely of Oxford and Tamas Szekely of the University of Bath call the study "ground-breaking." The two Szekelys suggest that behavioral and population researchers develop models to assess how demographic shifts like sex ratio might influence consumer behavior. The theory might have a particularly ripe testing ground in China, which will soon have a male surplus of 40 million, for an overall sex ratio of 1.2 men to every woman. Break out your yuan, gentlemen.