Tens of millions of people are currently enslaved around the world.

Modern slavery is a hidden crime, so it's hard to get robust numbers, but the Global Slavery Index estimated in 2014 that perhaps 36 million people were in a situation of modern slavery.

Given that modern slavery in its various forms is prohibited under international law and in almost every country, why is it so widespread and pervasive?

The reason is that modern slavery thrives when three factors intersect. These are:

1. The demand for extremely cheap labour

2. Individual vulnerability and marginalization

3. Weak rule of law.

Of course, there is nothing legally wrong about seeking lower labor costs, as long as this is done in compliance with the law. But when it comes to modern slavery the objective is to pay extremely low wages -- invariably in breach of the law.

Sadly, there is often a compelling economic model for this. It allows businesses to illicitly minimize their labour inputs- - usually the largest component of their operating costs -- and hence minimize the cost of producing goods and services, and thereby maximize their profits. Often it enables otherwise uneconomic businesses to remain viable -- at a massive social cost...