Countries with the most enslaved people

While many believe slavery is an issue of the past, it remains a real, yet largely hidden, problem. An estimated 35.8 million people are enslaved worldwide, according to a recent report by the Walk Free Foundation, a human rights organization.

Modern-day slavery differs from traditional slavery. In traditional slavery, which is illegal in each of the 167 countries reviewed in the 2014 Global Slavery Index, people were considered legal property. However, modern slavery, which is defined as possession or control of a person that deprives them of their rights with the intention of exploiting them, exists in each of the 167 nations.

In some countries, the number of enslaved people is especially high. Five countries alone account for 61% of all people believed to be living in modern slavery, and 70% of all enslaved people live in 10 countries. India had the highest number of people living in modern slavery, at over 14 million. Based on figures from the 2014 Global Slavery Index, these are the countries with the most slaves.

Many of the nations on this list are also among the world's most populous, which certainly plays a role in the high numbers of slaves. Seven of the world's 10 most highly populated nations are among the countries with the most people living in slavery. However, size alone does not account for the high levels of slavery in these nations. For instance, the United States is the world's third most populous country, yet it has far fewer people enslaved than any other similarly large country.

In fact, a number of the countries with the most slaves also have a high prevalence of slavery, measured as a percent of the population. For instance, more than 1% of the populations of India, Pakistan, and the Democratic Republic of the Congo were deemed by the Walk Free Foundation to be enslaved, a higher percentage than in most nations. In Uzbekistan, 4% of all people live in modern slavery, the second highest percentage in the world.

Populations that are vulnerable to slavery often reside in countries where government is not stable or discrimination is prevalent, according to the Walk Free Foundation. Fiona David, executive director of global research for the foundation, summarized the role of political instability in driving vulnerability, telling 24/7 Wall St., "In conflict situations, the rule of law breaks down. People no longer have access to the police or other services to protect them." Similarly, when discrimination is rampant, people also lack access to important protective services.

Vulnerability to slavery is also shaped by a country's economic and social development. In fact, the nations with the highest numbers of people living in slavery often had low scores on the Human Development Index (HDI). Seven of the 10 countries on our list had low HDI scores, falling outside the top 100 nations measured out of a total of 187 countries. One country that scored especially poorly was the Democratic Republic of the Congo, where a lack of stability has hampered development and, in turn, made people vulnerable to slavery.

Corruption also frequently hampers government policies and other efforts to curb modern slavery. According to David, people are more vulnerable when the rule of law is not strong enough to protect them, "and, of course, corruption breaks down the rule of law." Anti-corruption advocacy group Transparency International rated all but one of the countries on this list worse than a majority of countries on its 2013 Corruption Perceptions Index.

To identify the countries where the most people live in modern slavery, 24/7 Wall St. reviewed figures from The Global Slavery Index 2014 on the estimated population living in slavery in each country. The index also provided the approximate percentages of a country's population living in modern slavery. We also reviewed data from the United Nations Development Programme's Human Development Index (HDI). Economic data, such as gross domestic product (GDP) per capita, came from the International Monetary Fund (IMF). Data on corruption is from the 2013 Corruption Perceptions Index, compiled by Transparency International.

These are the countries with the most slaves.

1. India

> Est. population in modern slavery: 14.3 million
> Pct. population in modern slavery: 1.14% (5th highest)
> Human Development Index Score: 0.586 (46th worst)
> GDP per capita 2013: $5,450 (50th lowest)

With the second-largest population in the world, it is perhaps not surprising that India has the largest absolute number of residents living in conditions of modern slavery. The 14.3 million modern-day slaves in India, however, is by far the highest figure worldwide, and more than four times the next highest figure. The prevalence of slavery in India, as in other countries located in the Asia-Pacific region, is largely due to the economy's dependence on low-skilled and cheap labor. Bonded labor is especially prevalent in the country. Forced marriages and commercial sex workers are also relatively common. Like many other countries with large numbers of modern slaves, India is also quite poor. India had a GDP per capita of just $5,450 per capita last year, one of the lower figures worldwide.

2. China

> Est. population in modern slavery: 3.2 million
> Pct. population in modern slavery: 0.24% (59th lowest)
> Human Development Index Score: 0.719 (76th worst)
> GDP per capita 2013: $11,868 (77th lowest)

Roughly 3.2 million people live in modern slavery in China. This high figure may be due, in part, to the country's scale, as China is the world's most populous country with more than 1.3 billion residents. However, in the U.S., the world's third most populous country, just over 60,000 people live in modern slavery, according to the Walk Free Foundation. China's rapid modernization and urbanization, the foundation adds, "correlates with large flows of domestic migrants moving around the country in search of work." Last year, roughly 166 million workers in China left their hometowns and worked elsewhere, according to the National Bureau of Statistics of China. That figure alone is larger than the entire U.S. labor force. Such migrant workers, according to the foundation, are vulnerable to modern slavery in a range of industries, including construction and mining.

3. Pakistan

> Est. population in modern slavery: 2.1 million
> Pct. population in modern slavery: 1.13% (6th highest)
> Human Development Index Score: 0.537 (39th worst)
> GDP per capita 2013: $4,574 (44th lowest)

More than 1% of Pakistan's population — or an estimated 2,058,200 people — are believed to be living in slavery, both among the highest figures worldwide. The most common form of slavery in Pakistan is debt bondage, a technique frequently used by employers in ungoverned and fringe industries. As workers spiral further into debt, other family members are often forced to help work off the bond. According to the Walk Free Foundation, there are an estimated 10 million child workers in Pakistan. Forced marriages and sex trafficking are also more common in Pakistan than in the vast majority of countries.

4. Uzbekistan

> Est. population in modern slavery: 1.2 million
> Pct. population in modern slavery: 3.97% (2nd highest)
> Human Development Index Score: 0.661 (60th worst)
> GDP per capita 2013: $5,176 (48th lowest)

Roughly 4% of all people in Uzbekistan live in modern slavery, nearly the highest percentage in the world. According to Human Rights Watch, "State-sponsored forced labor of children and adults in the cotton sector continues on a massive scale," with over one million people forced to pick cotton for two months each year. The Cotton Campaign, an organization dedicated to eradicating forced labor in the Uzbekistani cotton industry, estimates that the number of citizens forced to pick cotton last year was as high as five million. Despite a decline in cotton production in recent years, and a drop in global prices, both the IMF and Asian Development Bank forecast strong growth in the country's economy in 2014 and 2015.

5. Russia

> Est. population in modern slavery: 1.0 million
> Pct. population in modern slavery: 0.73% (32nd highest)
> Human Development Index Score: 0.778 (57th best)
> GDP per capita 2013: $24,298 (46th highest)

Russia is one of just five countries in the world with more than one million people living as modern slaves, according to the Walk Free Foundation. These include laborers born in countries formerly part of the Soviet Union, as well as women and children who are trafficked as sex workers. The foundation is also quite critical of the Russian government's response to the problem, and notes that rampant corruption in law enforcement increases the vulnerability of Russians living in modern slavery. Russia's GDP per capita, at $24,298 last year, was higher than that of any other country with a similarly high number of modern slaves. However, declining oil prices and economic sanctions could curb Russia's economic growth.

24/7 Wall St. is a USA TODAY content partner offering financial news and commentary. Its content is produced independently of USA TODAY.