The United Nations’ definition of trafficking is:

The recruitment, transportation, transfer harbouring or receipt of person by means of 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 prostitution of others or other forms of sexual exploitation, forced labour services, slavery or practices similar to slavery, servitude or the removal of organs.

Sex trafficking is trafficking for the purpose of sex.

All sex trafficking crimes have two components: slave trading and slavery

Slave Trading: the process of acquiring, recruiting, harboring, receiving or transporting an individual, through any means and for any distance, into a condition of slavery or slave-like exploitation.

Slavery: the process of coercing labor or other services from a captive individual, through any means, including exploitation of bodies or body parts.

2 main causes for sex trafficking:

1- Extreme poverty

2- Economic Globalization. Globalization helped make present-day slaves easy to procure, easy to transport, and easy to exploit.

Reasons why anyone from small-time criminals to sophisticated organized crime groups do it?

1- To fill the growing demand for paid sex. Men may not know that they are buying sex from a slave, but they know that they are paying much lower prices than before, and in general only slave labor can facilitate those lower prices. Or put in another way: Demand for sex drives many consumers to prostitutes. Demand for low-cost sex drives them to slaves.

2- It’s a very lucrative business offering huge profitability with minimal risk due to corruption in law enforcement, border control and the judicial system in many countries; the lack of funding and focused law-enforcement on slave-related crimes; ineffective laws and minimal prosecution of sex traffickers.

4.2% of the world’s slaves are trafficked sex slaves, but they generate 39.1% of slaveholders’ profits. The global weighted average net profit margin of almost 70% makes it one of the most profitable enterprises in the world. By comparison, Google’s net profit margin in 2006 was 29% and Microsoft was 28.5%…

Maintaining sex slaves requires minimal effort who can be sold for services literally thousands of times before being replaced.

Reference: Siddharth Kara’s book: Sex Trafficking: Inside the Business of Modern Slavery