ECONOMISTS CLAIM to study markets in all their forms. But one, in particular, seems to make them blush: sex work. In a new book, “Sex Work by Numbers”, Stef Adriaenssens of KU Leuven, a university in Belgium, estimates that less than 5% of the 18,232 academic publications on the industry produced between 2000 and 2024 took an economic or business view. By comparison, 40% concerned biology or medicine, more than 25% related to psychology or psychiatry and almost 20% had to do with the law. A quick search for “sex work” or “prostitution” in the database of the National Bureau of Economic Research, a collection of working papers, generates just 178 results among 35,450 articles.
That is a big omission for what is a large industry. Porn alone is thought to generate almost $100bn in revenues a year worldwide, twice as much as AI. OnlyFans, a subscription site known for X-rated content, hosts 4.6m creators, many of them in adult entertainment. It has 380m users who together spend over $7bn a year. Estimates from UNAIDS, a UN agency, put the share of the world’s women aged 15 and over engaged in “exchange of sexual services” at 0.6%. In sub-Saharan Africa, this rises to 1.3%.
Sex work is, granted, difficult to study. It covers all manner of X-rated activities. A streetwalker in Nairobi, a high-end escort in London and a cam-girl in Kyiv inhabit utterly different economic worlds. Many switch between pornography, stripping and prostitution as demand requires. Criminalisation drives the industry underground. Even where it is legal, as in Germany and the Netherlands, stigma makes workers coy about discussing their trade.
Where facts and figures are scarce, people have regularly turned to guesswork. In the late 18th century a police magistrate put the number of prostitutes in London at 50,000—or one in five women in the city aged 15-40. Half a century later the Bishop of Exeter offered an equally hazy guess of 80,000. Even today policymakers routinely discuss the economic cost of sex work, in terms of crime and disease, confident in their conclusions but all too often cavalier about evidence.
Economists’ reluctance is, then, a pity. Sex work is, after all, a market shaped by supply, demand and price signals. Where they have tried, their methods can be creative and results revealing.
Take the number of sex workers. In 2021 economists at Rwanda’s health ministry and America’s Centres for Disease Control and Prevention borrowed the “capture-recapture” method from ecology to estimate a headcount. They handed out keyrings to randomly selected streetwalkers they encountered at known hotspots across the country, then returned a week later to offer bracelets to another random sample, this time asking if any of them had received a trinket the week before. (They came back the next week, too, for good measure.) The total number could then be worked out by comparing the different sets of results. The researchers concluded that between 9,000 and 23,000 women, or 0.1-0.35% of Rwanda’s female population, plied the trade.
Randomised controlled trials, the gold standard, are out of bounds for obvious ethical reasons (you cannot in good conscience expose some women to unprotected sex or violence). But economists can study natural experiments. In 2018 Scott Cunningham of Baylor University and Manisha Shah of the University of California, Berkeley, used a Rhode Island judge’s surprise decision to (in effect) decriminalise indoor sex work and found it led to a drop in both violent crime and female gonorrhoea cases. In 2020 Ms Shah and her co-authors considered the inverse situation after a district of East Java in Indonesia unexpectedly criminalised sex work. Sexually transmitted infections among sex workers rose, while women pushed out of the trade struggled to pay their children’s school expenses.
As sex work is being reshaped by policy and technology, economists are gaining new ways of tackling the research question. Governments are, helpfully, creating ready-made natural experiments by introducing new regulations. Belgium granted sex workers full employment protections in 2024 and Italy brought prostitution into the tax net last year, for example.
Meanwhile the internet is changing the nature of sex work and making it a bit easier to examine. Rather than tag and recapture Belgian and Dutch sex workers at the kerb, researchers at KU Leuven, including Mr Adriaenssens, looked at more than 24,000 reviews posted in a 12-month period in 2019-20 on hookers.nl, a popular online marketplace. By using a similar principle and maths as the researchers in Rwanda, they put the share of women aged 15-49 in the Netherlands and northern Belgium engaged in sex work at 0.15% and 0.18%, respectively.
These numbers look set to grow as platforms such as OnlyFans lower barriers to entry and attitudes towards sex work change. In Sweden, 8% of girls aged 15-19 say they have sent X-rated content or arranged to meet someone for sex in exchange for money. Only 56% of Britons aged 18-25 regard “sugaring”, when a younger person dates an older one for material benefits, as sex work, compared with 70% of over-65s.
In a paper published last year, Elias Carroni, Davide Dragone and Marina Della Giusta, three Italian economists, predicted that “digital sex”, such as online porn and virtual companionship, reduces the social and psychological cost of selling sex, as abundance erodes stigma. Replacing physical intimacy with the digital sort, they argued, may cause a slew of economic consequences, starting with a faster decline in fertility rates. Greater supply of sexual services may also cause prices to fall, further spurring demand. Only a very dismal scientist wouldn’t be interested in whether they are right. ■
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