We all know black market goods are available all over the world, but what you may not know is that if you add up all revenue generated from un-taxed business it would equal the second largest economy of the world, behind only the United States.

This off-the-books economy is referred to as System-D, a name that grew out of French speaking parts of Africa and the Caribbean where the practice has been prevalent for years. The D is short for débrouillard, a French word used to describe particularly effective and motivated people.

In 2012 nearly half of the worlds labor force is employed by System-D and those numbers are growing steadily, as are the revenues it generates.

On Around the World, Christiane Amanpour sits down with Journalist Robert Neuwirth, a pioneer in the study of the System-D economy and author of the book Stealth of Nations: The Global Rise of the Informal Economy