An estimated 40.3 million people suffer today in slavery. Living a shadowed existence between lawful states, victims yield their captors $150 billion in illegal profits every year. This most wretched of facts is made even more haunting when you consider that 1 in 4 victims are children.

"We know that if there are 40 million people in modern slavery, only tens of thousands of victims are being helped, assisted and supported, whether through the criminal justices system or through victim support systems," Fiona David, Walk Free Foundation's executive director of global research, told CNN. "It's a massive gap that we have to close."

Thanks to the efforts of governments and NGOs, that gap is closing.

There are fewer slaves in the world today, per capita, than at any other point in history. Chattel slavery, the kind that lead to the Atlantic slave trade, was once a human universal. Today, it is abolished and morally condemned. Other forms of slavery, such as child labor and forced marriage, are in decline. And the United Nations has set a target to end modern slavery by 2025.

We are closer to ending this morally bankrupt practice than at any point in our history. Will the final push come in the form of robotic automation?

Robots to end slavery?

The idea is simple enough. Slavery is an economic crime. Its perpetrators lure desperate and disenfranchised peoples with the promise of a livelihood. They then force their victims to do repetitive, physically demanding, and often dangerous work while cutting them off from any physical, social, and lawful means of escape.

By design, machines perform repetitive tasks without concerns for the dangers or physical demands. In richer countries, they are already employed in industries associated with chattel slavery abroad, such as mining, farming, and textiles. As the thinking goes: if automation were to become widespread and cost effective enough, it would eradicate the need for cheap human labor and render slavery economically inefficient.

At End Slavery Now, Cazzie Reyes details how such a future might play out. Currently, China's factories are losing their traditional source of cheap labor as worker wages and education levels rise. To address this labor gap, the country purchased 56,000 robots in 2014 and plans to rapidly increase factory automation.

As this shift continues, low-skilled workers may "be moved from completing routine to more value-added tasks" or even new jobs in robot manufacturing.

Robots may also challenge another form of slavery: sexual exploitation. In the Netherlands alone about 4,000 people are coerced into the sex trade every year. Worldwide 4.8 million people are sexually exploited with no means of escape, the vast majority young women and children.

But brothels have emerged in Europe and Japan that provide companionship with realistic sex dolls. In the U.S., Houston almost became the first city to open a robot brothel, but its city council banned renting sex dolls in October of last year (though businesses can still sell them for home use).

In Love and Sex with Robots, A.I. researcher David Levy argues that such institutions can reduce prostitution rates. As the dolls become more lifelike, he sees the world's oldest profession going the way of match girls and lamp lighters.

Futurists Ian Yeoman and Michelle Mars divine a similar future in their paper "Robots, men, and sex tourism." By 2050, they write, Amsterdam's famed red-light district will be dominated by hyper-realistic sex androids. The androids would not only allow the sex industry to grow but also curb the spread of STIs and improve the government's ability to regulate human trafficking.

Sold down the river

As automation spreads into new territories and industries, it may make slavery less economically efficient in the long run. In the short term, however, slavery will remain expedient, and economic expedience, not efficiency, has been a main driver of slavery throughout history.

That's the future predicted by Verisk Maplecroft's "Human Rights Outlook 2018" report.

The report estimates that over the next two decades, 56 percent of workers in ASEAN-5 manufacturing industries will lose their jobs to automation. With few skills and fewer options, displaced workers can become targets of the exploitative practices that lead people into slavery and human trafficking.

The ASEAN-5 countries already rank high on the Modern Slavery Index, and the report forecasts further deterioration. It is estimated that Vietnam alone could see 36 million people seeking new jobs in the coming decades, creating ample opportunities for human traffickers.

"Displaced workers without the skills to adapt or the cushion of social security will have to compete for a diminishing supply of low-paid, low-skilled work in what will likely be an increasingly exploitative environment," Alexandra Channer, Verisk Maplecroft's human rights strategy lead, said in a release. "Without concrete measures from governments to adapt and educate future generations to function alongside machines, it could be a race to the bottom for many workers."

Similarly, the belief that robotic sex workers will significantly reduce demand for sexual exploitation, let alone drive it to zero, is hardly universal. Opponents argue that sexual exploitation is as much about degradation as sex, that humans will always prefer other humans, and that there are lines that robotic sex peddlers won't cross but human traffickers will (i.e., the exploitation of children).

"So we're not just having a conversation here about objects that people rub on their genitals. This is not what this is about," Kathleen Richardson, director of the Campaign Against Sex Robots, told Feminist Current. "[Sex robots are] piggybacking off on those real lived experiences of real human women being dehumanized by the commercial sex trade."

Social and political death

Nor is slavery only an economic crime. It has many social and political causes that automation cannot address.

For example, North Korea has instituted a system of state-sanctioned force labor. Its government has arrested tens of thousands of people, typically for crimes against the state, and sentenced to work in labor camps. These prisoners work dangerous, long hours in mines, factories, and logging camps and may even be exported to places like China and Russia, where they yield North Korean leaders between $1.2 and $2.3 billion dollars annually.

While automation may, one day, reduce demand for North Korea's macabre exports, it is unlikely the totalitarian regime would do away with this system in the name of economic efficiency.

That's because this form of slavery is as much political as it is profitable. It removes dissidents from political life and places them in a type of social purgatory. Citizens who are tired, hungry, weak, and enslaved in a strange land make for poor revolutionaries.

Additionally, our modern definition of slavery has expanded to practices beyond chattel slavery. It now includes any practice that reduces a person to the statues of property and deprives them of their right to choose, such as forced marriage. However, forced marriage is as much a social and cultural transaction as it is an economic one. In countries that value such institutions, no machine could replace that form of social control.

Will automation be part of the solution?

Truth is, we don't know. As Pauline Oosterhoff, research fellow at the Institute of Development Studies, writes: "The fact is that we do not have a sure-fire way to eradicate slavery in the existing economy. We are not really sure what role previous rounds of automation have played in either eliminating or encouraging modern-day slavery, and we do not know what effects new developments in automation and artificial intelligence will have."

Automation may make reducing chattel slavery easier in some states, but it can't inoculate societies from the social and political ills that create opportunities for exploitation. According to the Council on Foreign Relations, contemporary abolitionists focus their efforts on these strategies:

Better law enforcement. Governments can better provide law enforcement with the tools to combat human trafficking and streamline the court processes and laws to make legal efforts more consistent and effective.

Transparent supply chains. Modern businesses have complex international supply chains that may intersect with slavery — some even argue it's impossible to make a smartphone that doesn't rely on child labor. In addition to transparency laws, abolitionist call for mandating supply chain investigations and making ethical sourcing a central business practice.

More comprehensive and widespread reporting. Reports that name governments, businesses, and individuals complicit in slavery help lessen demand as such public shaming leads to social opprobrium and economic consequences.

Public education. Exposing abuses to the public educates them on modern slavery practices. This can help at-risk communities from falling prey to exploitation, and move constituents to support funding rehabilitation and prevention programs.

Will these efforts close the slavery gap? It will be difficult, especially by 2025, but at no other point in history has the will and the means to do so existed in such abundance. And we have 40.3 million reasons to make sure we do.