From Psychology Today:
In 2005, a team of British scientists published a paper in Human Nature wherein they analyzed the sexiness of women’s clothing as depicted in the magazine UK Vogue covering the period 1916 through 1999. They found that as the economic conditions worsened, women’s fashion styles became more provocative. They argued that to the extent that many women utilize their physical looks as sexual signals in the mating arena, one should expect that intra-sexual competition would yield a pressure for greater “sexual advertisement” in tough economic times.
(h/t Eric Barker)