The Asia Catalyst report portrays custody and education as a vast moneymaking enterprise masquerading as a system for rehabilitating women. Established by China’s legislature in 1991, the detention centers are run by local public security bureaus, which have the final say on penalties. Former inmates say police officials sometimes solicit bribes to release detainees.

The government does not publish regular statistics on the program, but experts estimate that 18,000 to 28,000 women are sent to detention centers each year. Inmates are required to pay for food, medical exams, bedding and other essential items like soap and sanitary napkins, with most women spending about $400 for a six-month stay, the report said.

“Those who couldn’t pay were only given steamed buns to eat,” one woman told Asia Catalyst.

At some centers, visitors are required to pay an entry fee of $33 to see imprisoned relatives.

Those who have studied the system say that local public security bureaus earn a sizable income from what is essentially free labor.

The Chinese government’s approach to prostitution is inconsistent. After the Communist victory in 1949, Mao Zedong made the rehabilitation of prostitutes, whom the Communists saw as victims of capitalist exploitation, a priority. During his first years in power, he effectively eradicated the trade. But the introduction of market overhauls in the early 1980s led to a resurgence in prostitution, and up to six million women were estimated to be working in the sex industry in recent years, according to a United Nations report.

Today, Chinese cities are full of “hair salons” with curtained-off back rooms and no visible scissors; at upscale karaoke parlors, young female attendants double as call girls. The police are often paid to look the other way, many prostitutes say.

But that apparent forbearance evaporates during periodic “strike hard” campaigns in which large numbers of prostitutes are rounded up, often before important political meetings. A police official in Liaoning Province told Asia Catalyst that cities and counties were required to meet quotas, prompting occasional “vice sweeps” to replenish jailhouse workshops.