Statistics on human trafficking from around the world:
$32 billion is spent on human trafficking.
Wikipedia says that "nearly 2.5 million people from 127 different countries are being trafficked into 137 countries around the world."
The U.S. State department releases a report every year about the black market in humans called The Trafficking in Persons report. The report has statistics on human trafficking in countries around the world.
Human trafficking is:
(a) [...] the recruitment, transportation, transfer, harbouring or receipt of persons, by means of the threat or use of force or other forms of coercion, of abduction, of fraud, of deception, of the abuse of power or of a position of vulnerability or of the giving or receiving of payments or benefits to achieve the consent of a person having control over another person, for the purpose of exploitation. Exploitation shall include, at a minimum, the exploitation of the prostitution of others or other forms of sexual exploitation, forced labour or services, slavery or practices similar to slavery, servitude or the removal of organs.