According to Anti-Slavery International there are:

• 27 million slaves in the world
• The largest number of people that has ever been in slavery at any point in world history.
• The smallest percentage of the total human population that has ever been enslaved at once.
• Reducing the price of slaves to as low as US$40 in Mali for young adult male labourers, to a high of US$1000 or so in Thailand for HIV-free young females suitable for use in brothels (where they invariably contract HIV). This represents the price paid to the person, or parents.
• This represents the lowest price that there has ever been for a slave in raw labour terms—while the price of a comparable male slave in 1850 America would have been about US$1000 in the currency of the time, that represents US$38,000 in today’s dollars, thus slaves, at least of that category, now cost only one one-thousandth (0.1%) of their price 150 years ago.

Around 20,000 and 40,000 people are trafficked into the United States each year - mostly as slaves in the sex industry.

A US Government report published in 2003 estimates that between 800,000 and 900,000 people worldwide are trafficked across borders each year, the majority in South East Asia, Japan, Russia and Europe.

To help prevent this you can visit Amnesty International.