Although slavery is now illegal everywhere, there are still about 30 million slaves worldwide according to the Global Slavery Index. Many are held in bonded servitude, particularly after taking loans they could not repay. Other are trafficked or forced to engage in prostitution. A person is a slave for an average six years, after which the person usually escapes, repays the debts holding them, or dies. Most of the world’s slaves are in South Asia (source). Almost half of all slaves worldwide are in India – or about 14 million people. That’s 1% of the Indian population. There are about 60,000 slaves in the United States (source). 4% of people in Mauritanian are slaves.
One form of modern slavery is sex trafficking. This involves the use of force, fraud or coercion to transport an unwilling victim into sexual exploitation. It’s incredibly hard to have good numbers on this since you want to exclude willing professionals who are simply traveling in search of a better income. But how do you know which prostitute is willing and which isn’t? The best available estimate – meaning the one that’s least wrong – tells us that globally 1 million girls and women are trafficked into brothels annually, and that 10,000 to 20,000 sex slaves are brought into the U.S. annually. The UNODC estimates the number of victims of human trafficking at any one time at 2.5 million, 80% of those are women trafficked as sex slaves (the rest as slaves in homes or sweatshops).
However, those numbers could be totally off the mark (source, source). Usually, the numbers are extrapolated on the basis of the numbers of known cases, i.e. cases that have ended up with the police or in court. As victims of sex trafficking are particularly well hidden (it’s a type of crime that’s vastly underreported since the victims are under total control by their bosses) you need to multiply the known cases by a certain number, but that number is by definition a very rough guess.
Hence the large differences between estimates:
Similar caveats are necessary for other types of forced labor that don’t involve prostitution and/or international trafficking (source).
The International Labor Organization has a lower estimate:
It’s hard to believe, but at this very moment an estimated 10% to 20% of the population of Mauritania – 340,000 to 680,000 people – still live in slavery. This is despite the fact that in 2007, the country became the last in the world to outlaw the practice. Anti-slavery activists are arrested and the government acts as if there is no problem. Only one slave owner has been successfully prosecuted.
It’s the nuances of a person’s skin color and family history that determine whether he or she will be free or enslaved. Most slave families in Mauritania consist of dark-skinned people whose ancestors were captured by lighter-skinned Arab Berbers centuries ago. Slaves typically are not bought and sold — only given as gifts, and bound for life. Their offspring automatically become slaves, too.
There’s also the North Korean gulag system, which holds 200,000 people. It’s essentially a constellation of slave-labor camps.
In Haiti, it’s estimated that there are 250,000 children working as unpaid domestic servants after their parents, who cannot afford to raise them, give them away. The child slaves in question are not called slaves; they’re called restaveks (derived from the French rester avec meaning “to stay with”) (source).
There’s an interesting database about modern slavery here.
Some data about human trafficking in the EU:
Here’s an historical perspective: