Surprisingly, the perpetrators behind human trafficking around the world are often women, the U.N. reported Thursday.

Women are the majority of traffickers in almost a third of the 155 nations the U.N. surveyed. They accounted for more than 60 percent of the human trafficking convictions in Eastern Europe and Central Asia.

For many, human trafficking is a world they had been pulled into themselves.

"Women commit crimes against women, and in many cases the victims become the perpetrators," Antonio Maria Costa, director of the Vienna-based U.N. Office on Drugs and Crime, said in an interview. "They become the matrons of the business and they make money. It's like a drug addiction."

Most of the world's nations reported some form of "modern slavery" last year involving mainly the sex trade or forced labor.

And the number of victims should grow as the global financial crisis deepens, Costa said.

The report by Costa's office was based largely on human trafficking convictions reported to the U.N. between September 2007 and July 2008. About 22,500 victims were rescued during that time. About four of every five reported cases involved sexual exploitation; most of the rest involved forced labor.

But Costa's agency gave no overall figures for how many millions of people might be affected. He said most countries' conviction rates for human trafficking rarely exceed 1.5 per 100,000 people.

Two of every five countries covered in the report had not recorded a single conviction from 2007 to 2008.

"Either these countries are blind to the problem or they are ill-equipped to deal with it," Costa said.

"We only see the monster's tail," he said. "How many hundreds of thousands of victims are slaving away in sweatshops, fields, mines, factories, or trapped in domestic servitude? Their numbers will surely swell as the economic crisis deepens the pool of potential victims."

The report's release coincided with the appointment Thursday of Academy Award-winning actress Mira Sorvino as a U.N. goodwill ambassador to help Costa's office fight human trafficking. Sorvino, who graduated magna cum laude from Harvard University in 1989 with a degree in Chinese, won an Oscar for best supporting actress in 1995's "Mighty Aphrodite."

"Until a few years ago, I blissfully believed that slavery was a thing of the past. ... Well, obviously I was terribly wrong," she said after Costa draped a blue-ribboned medal around her neck.

Sorvino told how the stories of trafficked children hit her particularly hard since becoming a mother with two young children herself.

"If slavery is not wrong, nothing is wrong," she said, repeating a famous statement by Abraham Lincoln, whose 200th birthday was celebrated Thursday.

The report also pointed out that women and girls suffer most from sexual abuse. About 20 percent of victims globally were children, mainly in Southeast Asia's Mekong region and parts of Africa.

Costa, who serves as the U.N.'s chief crime fighter, said it's difficult to get nations to address human trafficking because "it's at the crossroads" of other complex occurrences such as human migration and prostitution.

Sixty-three percent of the nations in the report had adopted some laws against human trafficking. The U.N. said most did so only after its protocol against human trafficking entered into force in December 2003.