Planning for freedom – how statistics can help us eradicate modern slavery

26 Feb 2018 16:08:52.343

PA 35/18

Experts in modern slavery from the University of Nottingham are using a new way of calculating the precise number of slaves in a city, region or country, helping the fight for freedom.

Working with the Home Office, Professor Kevin Bales CMG and Professor Sir Bernard Silverman from the Rights Lab at the University of Nottingham have successfully used a technique known as the Multiple Systems Estimate (MSE) to calculate a reliable estimate of the true number of slaves in a specific location.

Slavery is illegal in every country, which makes finding modern slaves very difficult. This exploitative crime, which affects over 40.3 million people globally, can take the form of forced marriage, forced labour, forced sexual exploitation and child soldiers.

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A well-hidden problem

Where slavery laws are well enforced, slaves are especially well hidden, making it hard to know how to best find and free them. Not knowing how many slaves exist means governments don’t know how much money should be allocated to fight the crime.

Because of its complex nature, modern slavery cannot be measured in the usual way we measure most crime, which involves surveying a sample of the general population to determine how many of them have been victims of different crimes. Political sensitivities, unwillingness to share data and questionable collection methods have led to inaccurate calculations of the prevalence of slavery and inadequate prevention efforts.

Now, researchers at the Rights Lab are using MSE so that organisations can better understand the scale of the issue and help communities to step up in their fight against slavery.

Understanding the true extent of modern slavery

Using this system, lists of trafficked or enslaved people are collated from different organisations such as NGOs, local government and the police. These lists are then compared to check the information and identify any overlaps. These numbers and overlap totals are then entered into a formula which generates a reliable estimate of the number of slaves within a specific area.

Professor Silverman, a world-leading statistician, and a lead researcher on the project at the Rights Lab, said: “Interestingly, a form of MSE was used as long ago as the seventeenth century to estimate human populations, and it was rediscovered in the early twentieth century by ecologists counting turtles, wild fowl and tsetse flies. It’s since been used in a number of human rights violations contexts. In Guatemala it was used to calculate the number of killings in the 36 years of armed conflict, and in Peru MSE estimates tripled the previously conservative estimate of killings in the civil war.

“It was first used to address modern slavery in 2014 in the UK, generating an estimate of 10,000 to 13,000 trafficked/enslaved people within the country at a time when there were previously only 2,744 known and recorded cases. We wanted to further develop this work and come up with a method of calculating slaves in any specific area of the world.”


The team used MSE in New Orleans in 2017 as a pilot, where NGOs, governmental and law enforcement partners collaborated to understand the extent of slavery taking place within their communities.

Eight organisations agreed to share information for comparison. Altogether the eight lists contained information of 185 people who had been caught up in trafficking/slavery in the year 2016.

By comparing overlaps and putting those numbers into the formula, MSE provided an estimate of 997 victims of modern slavery in 2016, which suggests that the true number of trafficked people in the city is five times higher than the known cases.

The technique has also been adopted by governments in the Netherlands and Spain as well as by the Walk Free Foundation and the UN Office on Drugs and Crime who are using it in Eastern European countries. The method and its findings have been widely accepted by the International Labour Organisation and the International Organisation for Migration.

‘With the facts, we can plan for freedom’

Professor Kevin Bales, a world-leading expert in modern slavery, the Rights Lab Research Director and one of the researchers who devised this new approach, said: “The powerful spotlight of MSE shines wherever lists of survivors can be brought together to measure overlaps. With fresh knowledge, a city, country, or nation can better plan a response to modern slavery. With the facts, we can all plan for freedom, and using MSE has never been easier.

“The Rights Lab is ready to help any NGO, city or government use their existing data to find a reliable estimate of modern slavery within their boundaries.”

This work has been supported by the ESRC and AHRC PaCCS Transnational Organised Crime grant – Modern Slavery: Meaning and Measurement.

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Notes to editors: 

The University of Nottingham is a research-intensive university with a proud heritage, consistently ranked among the world's top 100. Studying at the University of Nottingham is a life-changing experience and we pride ourselves on unlocking the potential of our 44,000 students - Nottingham was named University of the Year for Graduate Employment in the 2017 Times and Sunday Times Good University Guide, was awarded gold in the TEF 2017 and features in the top 20 of all three major UK rankings. We have a pioneering spirit, expressed in the vision of our founder Sir Jesse Boot, which has seen us lead the way in establishing campuses in China and Malaysia - part of a globally connected network of education, research and industrial engagement. We are ranked eighth for research power in the UK according to REF 2014. We have six beacons of research excellence helping to transform lives and change the world; we are also a major employer and industry partner - locally and globally.

Impact: The Nottingham Campaign, its biggest-ever fundraising campaign, is delivering the University’s vision to change lives, tackle global issues and shape the future. More news…



Story credits

More information is available from Angharad Smith, Research Assistant at the Rights Lab at the University of Nottingham

Charlotte Anscombe – Media Relations Manager (Arts and Social Sciences)

Email:  Phone:+44 (0)115 74 84 417 Location: University Park

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