Modern slavery is a global issue. Here's why

North Korea and Eritrea have the world's highest rates of modern slavery, said a global survey on Thursday that highlighted how conflict and government repression are the main drivers of a crime estimated to affect more than 40 million people worldwide.

The Central African nation of Burundi also has a high prevalence of slavery, according to the 2018 Global Slavery Index published by the human rights group Walk Free Foundation.

"Each of these three countries has state-sponsored forced labor, where their government puts its own people to work for its own benefit," said Fiona David, research chair of Minderoo Foundation, which led the data collection.

More than 40 million people were enslaved around the world as of 2016, according to an estimate by the Walk Free Foundation and the United Nations' International Labour Organization (ILO).

India was home to the largest total number with an estimated 8 million slaves among its 1.3 billion population, according to Walk Free's 2018 calculation.

Two years ago, the index showed 18.3 million people living in modern slavery in India. The difference is due to changes in methodology, Walk Free said, reflecting ways of counting people enslaved on any given day or over a longer time period.

China, Pakistan, North Korea and Nigeria rounded out the top five nations with the largest number of slaves, accounting for about 60 percent of victims globally, according to Walk Free.

But North Korea had the highest percentage of its population enslaved, with one in 10 people are in modern slavery and "the clear majority forced to work by the state", the index said.

Researchers interviewed 50 North Korean defectors who spoke of long hours and inhumane conditions in forced unpaid labor for adults and children in farming, construction and roadbuilding.

"This index makes us visible," said Yeon-Mi Park, a defector who spoke at a news conference at United Nations headquarters.

"These people simply were born in the wrong place, and that's what they are being punished for," she said, describing being trafficked into China where she was sold as a child bride.

Another defector Jang Jin-Sung said North Koreans do not consider themselves slaves.

"They've been indoctrinated all their lives to think that whatever they do for the state is a good thing," he said.

In Eritrea, the report said the government is "a repressive regime that abuses its conscription system to hold its citizens in forced labor for decades".

Burundi's government also imposes forced labor, Walk Free said, while rights groups including Human Rights Watch have implicated its security forces in murders and disappearances.

Other countries with the highest rates of slavery were the Central African Republic, Afghanistan, South Sudan and Pakistan.

"Most of these countries are marked by conflict, with breakdowns in rule of law, displacement and a lack of physical security," the report said.

With more than nine million people living in slavery - nearly eight in every 1,000 people - Africa had the highest rate of enslavement of any region, according to the report.

The researchers also warned that consumers in affluent countries may be purchasing billions of dollars worth of products manufactured with slave labor, including computers, mobile phones and clothing.

"Modern slavery is a first-world problem," said Andrew Forrest, a co-founder of Australia-based Walk Free. "We are the consumers. We can fix it," he added.

Slavery is likely more widespread than the research suggests, activists and experts say. The report noted gaps in data from Arab states, as well as a lack of information on organ trafficking and the recruitment of children by armed groups.