It is a business that exists in the shadows. You won’t see a billboard for a domestic slave, nor a glossy magazine spread for the latest in forced labor. While cities struggle to rid their streets of prostitutes, they forget these people are victims of crime. Yet, make no doubt: human trafficking is big, big business.

The International Labor Organization (ILO), a United Nation’s agency dealing with labor issues, has released a report makes clear the financial aspects of human trafficking. The report takes some time to clearly define human trafficking/forced labor, stating that this includes debt bondage, but makes clear that things like mandatory military service does not constitute forced labor.

With that, the ILO says human trafficking accounts for $150 billion of annual global profit. That’s more than tobacco ($35B), Google ($50B), Big Oil ($120B) and even the U.S. banking system ($141.3B). It is most profitable in economically-stable, developed areas, such as those of the European Union and the United States. Sexual exploitation is the most profitable form of human trafficking but the mon form of trafficking is labor in areas such as agriculture, manufacturing, mining and domestic service.

The report states that women and girls make up about 55 percent of trafficking victims. Adults are more trafficked than children, mainly for labor work. The report cites this example:

Some cases on construction sites in Eastern Europe, for example, relied on both deception and corruption. Migrant workers are brought illegally to work on a construction site, without knowing the working conditions or terms of payment. There, they discover that they are forced to live together in a remote place provided by the employer (to avoid police controls) and told that they will be paid only at the end of the construction. A few days before the end, when the work is done and wages are due, the owner may call a law enforcement officer to inform him of the presence of irregular migrants. The workers are then deported and the employer does not need to pay them. All due wages (minus the bribe) increase the profits made, thanks to the work of the abused migrants.

The report also points out that it is difficult to quantify much of the impact of human trafficking, especially sexual exploitation. The victims often do not report the crime, even if they are able, and due to the nature of this “business,” solid financial reporting does not exist.

Poverty is a driving force for human trafficking: the most vulnerable people with the fewest economic choices are easy prey for traffickers. Low rates of education and lack of rule of law and property rights also contribute. The ILO concludes:

The need to address the socio-economic root causes of this hugely profitable illegal practice is urgent. Comprehensive measures are required that involve governments, workers, employers and other stakeholders working together to end forced labour. The continued existence of forced labour is bad for its victims, for business and development. It is a practice that has no place in modern society and should be eradicated as a matter of priority.

Because human trafficking is such a profitable business, it is difficult to fight. Like drug cartels, traffickers are good at adapting their work to skirt law officials. They are not going to easily give up such a profitable business. However, as the ILO points out, the cost of human trafficking is too high to ignore. One person enslaved is one too many.

Read the ILO’s full report here.