This is not about economic fluctuations or long cycles like Kondratieff cycles, this is about the sexual practice of partner exchanges or group sex. This practice that started in US military families in World War II has now spread world-wide, first as wife swapping than with women's emancipation into couple exchanges that a organized through websites or swinging clubs. Estimates vary widely, but somewhere between 1 and 15% of the population practices it.
Fabio d'Orlando tries to explore the economics of swinging. In the absence of much data and theory about it, he draws heavily on Jeremy Greenwood and Nezih Guner's theory of the emergence of premarital sex (discussed here) and modifies it to a theory of increasing kinkiness of sex. I did not think this was very inspiring in this paper, but a (long) footnote caught my eye.
Swinging clubs charge an entrance fee, which depends on who enters. Couples pay, say, $50, but single men $150. This is more than a night with a prostitute, but single men seem to value of having sex with a woman who does not fake it. Single women, however, are typically not allowed in on the premise that they are prostitutes. The interesting bit is how a swinging club owner should maximize profits, given that couples are more likely to come if there are fewer single men. Given the hidden nature of this market and thus the lack of information, it would interesting to see the diversity of outcomes.