"While the information vacuum poses challenges, we are confident that the data reflects the most accurate estimation on the pervasiveness of modern-day slavery inside North Korea", said Ms Fiona David, Walk Free's executive director of global research, noting that the research had also involved looking at a variety of pre-existing data from worldwide organisations and non-profit organisations. The US number, the study estimates, is nearly one hundredth of the estimated 40.3 million global total number of people it defines as being enslaved. Researchers were able to sit down with 50 North Korea defectors, all but one of whom said they were subjected to forced labor.
Modern slavery estimates for the US, Australia, Britain, France, Germany and the Netherlands were also higher than previously thought, but these countries were taking the most action to tackle slavery, the report noted.
"This index makes us visible", said Yeon-Mi Park, a defector who spoke at a news conference at the United Nations headquarters.
Last year, it joined with the UN-affiliated International Labour Office (ILO) to release a report that estimated 40.3 million people were in some form of modern slavery around the world on any given day last year.
"They've been indoctrinated all their lives to think that whatever they do for the state is a good thing", he said. The Index revealed that today, more than 400,000 people are working as modern slaves in the United States.
The index was compiled by the Walk Free Foundation, an anti-slavery organization founded by Australian mining billionaire Andrew Forrest.
"For example, we know that criminals involved in these types of exploitation are going into online spaces to enable their criminality", the NCA's deputy director added in a statement. Furthermore, the reports show "more than a third of victims of modern slavery are victims of forced marriages". US consumer demand is key to fueling this supply, with electronics, garments, fish, cocoa and timber the highest value categories of imported items.
These countries - particularly the UK, Netherlands and the U.S. - are doing the most to tackle slavery at home, says the report, through initiatives such as the UK's Modern Slavery Act.
China was by far the largest source of at-risk goods, with the United States importing ($122bn) of electronics and clothing from the country.
"By unraveling the trade flows and focusing on products at risk of modern slavery that are imported by the top economies, it becomes clear that even the wealthiest countries have a clear and immediate responsibility for responding to modern slavery both domestically and beyond their borders", the report said.
"Unfortunately, due to the limits of existing data, it was not possible for the Global Estimates of Modern Slavery to measure and include the scale of trafficking for organ removal or the recruitment child soldiers", The Global Slavery Index concludes.