Something we discussed last night on our radio program was how women's menstrual cycles and our pheromones affect our sexual attraction to others, and their attraction to us. Studies have shown that when women are ovulating (fertile), men find them more attractive. Naturally, when a woman is on a hormonal contraceptive (such as the birth control pill), it suppresses ovulation and thus does not achieve the same effect.
While cruising the internet today, I came across a study from 2007 that found that lap dancers make more money in tips when they are ovulating. Here's a clip from the study abstract:
...we examined ovulatory cycle effects on tip earnings by professional lap dancers working in gentlemen's clubs. Eighteen dancers recorded their menstrual periods, work shifts, and tip earnings for 60 days on a study web site. A mixed-model analysis of 296 work shifts (representing about 5300 lap dances) showed an interaction between cycle phase and hormonal contraception use. Normally cycling participants earned about US$335 per 5-h shift during estrus [ovulation/fertile], US$260 per shift during the luteal phase [infertile], and US$185 per shift during menstruation. By contrast, participants using contraceptive pills showed no estrous earnings peak. These results constitute the first direct economic evidence for the existence and importance of estrus in contemporary human females, in a real-world work setting. These results have clear implications for human evolution, sexuality, and economics.