Global Slavery Index

Frequently asked questions


What is the Global Slavery Index?

The Global Slavery Index is Walk Free’s flagship report that examines a complex issue– modern slavery. Modern slavery is often hidden, so it is important that we measure it to better inform effective action to address it. The Global Slavery Index remains the only research of its kind to measure the number of people living in modern slavery country by country. The Global Slavery Index is a tool for citizens, civil society, businesses, and governments to understand the scale of the problem, existing responses, and contributing factors so that they can advocate for and build sound policies to eradicate modern slavery.

This report, the fifth edition of the GSI, shows how the compounding crises of the last five years have impacted modern slavery and provides a road map for actions to eradicate it.

What is modern slavery?

Modern slavery refers to situations of exploitation that a person cannot refuse or leave because of threats, violence, coercion, deception, or abuses of power. It takes many forms and is known by many names — forced labour, forced marriage, debt bondage, sexual exploitation, human trafficking, slavery-like practices, forced or servile marriage, and the sale and exploitation of children.

What is the difference between slavery and modern slavery?

Slavery has by no means been relegated to history. One difference between modern and historical slavery is that historical slavery was often sanctioned and protected by legal frameworks. Today most countries in the world have criminalised one form of modern slavery, be it slavery, slavery like practices such as debt bondage or forms of forced marriage, human trafficking or forced labour. However, we can see the legacy of historical slavery in modern slavery where entrenched power imbalances have led to the marginalisation and discrimination of certain groups who remain more vulnerable to modern slavery.

What are the main differences between the 2023 report and the last report in 2018?

The 2023 Global Slavery Index is underpinned by an updated dataset which is much larger than the 2018 edition. The estimates presented in 2023 draw on a greater number of representative national surveys – 75 in 2023 compared with 54 in 2018. While the methodology for the prevalence estimates remains similar to the last edition, including using the regional totals from the Global Estimates as the starting point, improvements in the Global Estimates methodology – for example, we improved the way we estimated for countries where no surveys have been conducted –– has flowed through to our national estimates in the GSI.

Is modern slavery getting better or worse?

Our Global Estimates of Modern Slavery produced in partnership with the International Labour Organization and International Organization for Migration point towards a worsening situation, with nearly 10 million more people in modern slavery in 2021 than in 2017. This increase reflects a real rise in modern slavery linked to increasing vulnerabilities as well as an improved understanding of the situation.

Why is the number of people in modern slavery increasing instead of decreasing?

In recent years, compounding crises – pandemics, armed conflicts, and the climate crisis – have led to unprecedented disruption to employment and education, increases in extreme poverty and distress migration, and an upsurge in reports of gender-based violence, together serving to heighten the risk of all forms of modern slavery.

How is climate change linked with modern slavery?

Climate change is not just an environmental issue, it’s inextricably linked to human rights. Its effects may push people to migrate and magnify drivers of displacement such as loss of livelihoods, food insecurity, and a lack of access to water and other natural resources. Migration in these contexts can be unplanned, more precarious, and expose people to higher risks of modern slavery.

The impact of climate change hits hardest those who are already in precarious situations, such as women, children, indigenous people, LGBTQI+ individuals, and members of marginalised communities, increasing their vulnerability to modern slavery.

Modern slavery is also linked to environmentally degrading industries that contribute to climate change. For example, forced labour is pervasive in industries driving deforestation around the world. Conversely, there is increasing evidence that renewable industries vital to our urgent transition to clean energy are also reliant on forced labour for the mining, processing, and manufacturing of critical minerals and inputs.

Which factors cause vulnerability to modern slavery?

As is usually the case, it is those who are already in situations of great vulnerability, dealing with poverty and social exclusion, who are most affected. It also mostly affects people who work in the informal economy, irregular or otherwise unprotected migrant workers, people subject to discrimination, and those living in contexts of crisis, such as armed conflicts and natural disasters. As a result of COVID-19 pandemic, unprecedented disruption to employment and education, increases in extreme poverty and distress migration, and an upsurge in reports of gender-based violence, together served to heighten the risk of all forms of modern slavery.

Why does Walk Free collaborate on the Global Estimates of Modern Slavery with the United Nations, but not on the Global Slavery Index?

Recognising the need for a unified estimate on modern slavery, the International Labour Organization, Walk Free, and the International Organization for Migration jointly produce the Global Estimates of Modern Slavery. While Walk Free, ILO and IOM worked together on the Global Estimates of Modern Slavery, the Global Slavery Index is the work of Walk Free alone.

Walk Free and ILO have different organisational objectives and this is reflected in our different approaches to national estimation. The ILO works in close collaboration with many national departments of statistics on forced labour or child labour surveys, upon request from their national authorities. While this approach is important, by working independently, Walk Free is able to produce national estimates for 160 countries.


How does the methodology differ to 2018?

In 2023, our estimates of modern slavery are based on a significantly larger dataset than in 2018, consisting of 75 national surveys on modern slavery. 71 surveys are conducted through the Gallup World Poll, and four national surveys are on forced marriage in the Arab States region – a data gap we acknowledged in 2018. The analysis of prevalence for the Arab States region also drew on representative surveys of migrant workers in the Arab States in six origin countries, strengthening our understanding of forced labour in the region. Our framework for measuring a strong government response to modern slavery has also expanded, with the number of indicators increasing to 141.

What was the scale of the research?

The GSI 2023 draws on the largest survey of its kind ever conducted, covering 75 countries. A mix of face-to-face and telephone interviews with almost 110,000 respondents revealed that men, women, and children were exploited in 129 countries, including high rates of exploitation in many developed countries.

Our measurement of governments’ efforts is also important. This draws on close to 25,000 data points sourced from 176 countries. Additionally, our assessments of vulnerability for 160 countries combined with our surveys allows us to produce estimates of modern slavery beyond those countries surveyed. All of this gives us the clearest picture yet of what is an inherently hidden problem – modern slavery.

How do you measure prevalence?

The Global Estimates of Modern Slavery regional estimates form the starting point for the 160 national level estimates presented in the Global Slavery Index. To get from regional counts to national estimates, statistical risk modelling produced country-level predicted probabilities of modern slavery based on individual and country-level risk factors for forced labour and forced marriage. Individual level risk is informed by nationally representative surveys conducted through the Gallup World Poll. Country-level risk is derived from Walk Free’s assessment of a country’s level of vulnerability. The regional totals in the most recent version of the Global Estimates were apportioned based on each country’s average predicted probability of modern slavery, taken from our risk modelling. Final adjustments are made for level of migration in and out of each country, state imposed forced labour, and an adjustment for the Arab States to integrate additional data.

Has the way you estimate prevalence changes since 2018?

The overall approach to prevalence estimation in 2023 remains the same as that of 2018 and involves risk modelling based on individual and country level risk factors, apportioning regional totals from the Global Estimates of Modern Slavery according to these risk factors, and post model adjustments based on strong evidence that couldn’t be captured through the risk model. An additional adjustment in 2023 was to countries in the Arab States region to account for heightened risk experienced by migrants unlikely to be accessed through surveys. Our national surveys of returned migrant workers in six origin countries across Asia and Africa inform the adjustments for the Arab States.

Why don’t you disaggregate estimates of modern slavery by type of modern slavery or demographic traits such as gender?

To produce reliable estimates disaggregated by type of modern slavery or demographic factors such as gender or age requires enough cases identified per country in each category of the factor you want to disaggregate by (for example, males and females). Given the relatively small sample sizes (around 1,000 per country) combined with the difficulty identifying this hard-to-reach population, we currently do not have sufficient data to be able to produce these breakdowns. We hope to have enough data to do this in the future. We encourage governments to conduct national surveys with large enough sample sizes to be able to disaggregate by characteristics of interest.

How did you come up with estimates for the other countries that were not surveyed?

The regional counts of modern slavery from the Global Estimates form the starting point for the national estimates of modern slavery presented in the Global Slavery Index. These regional estimates are informed, in large part, by the 75 national surveys on modern slavery conducted by Walk Free and the ILO. To develop the Global Slavery Index, we developed a model that incorporates national and individual level risk factors for every country in the Index. These factors include gender, age, and income (among others) and country level factors such as governance issues and level of inequality. The resulting risk scores from this model are then used to apportion the regional estimates to countries within that region. Walk Free then makes adjustments for level of migration in and out of each country, state imposed forced labour, and an adjustment for the Arab States to integrate additional data.

Why does Walk Free use extrapolation as part of its methodology?

In 2023, the national estimates in the Global Slavery Index rely on a greater number of surveys, requiring less extrapolation than in the previous edition. However, extrapolation allows us to estimate prevalence for non-survey countries. While extrapolation does introduce some error, improvements were made to the way we extrapolate in the Global Estimates which provides the starting point for the national estimates presented in the Global Slavery Index. To completely avoid extrapolation would require all governments to conduct national surveys.

How do you define modern slavery in your surveys?

We operationalise modern slavery in our surveys by focussing on two key components of modern slavery – forced labour exploitation and forced marriage.

Isn’t defining modern slavery simply in terms of ‘forced labour exploitation’ and ‘forced marriage’ restrictive?

Modern slavery covers a set of specific legal concepts including forced labour, concepts linked to forced labour (i.e., debt bondage, slavery and slavery like practices and human trafficking) and forced marriage. Although modern slavery is not defined in law, it is used as an umbrella term that focuses attention on commonalities across these legal concepts. Essentially, it refers to situations of exploitation that a person cannot refuse or leave because of threats, violence, coercion, deception, and/or abuse of power. To make this set of complex legal concepts measurable, the global estimates focus on two key forms of modern slavery: forced labour exploitation and forced marriage.

How accurate are the estimates of modern slavery and can they be trusted?

The estimates are largely derived from probabilistic nationally representative surveys which remain the current gold standard for estimating prevalence of modern slavery. Nonetheless, they are estimates and, as with all sample-based estimates, there is an accepted level of uncertainty. These estimates are likely to be an underestimate of the actual size of the problem. Given the sensitive nature of the topic, there is underreporting during surveys. We also only partially capture experiences of children and institutionalised populations. Walk Free continues to be dedicated to improving what is already a robust methodology.

How do household surveys reach people in modern slavery?

We have designed our surveys to collect information on experiences of forced labour exploitation and forced marriage that occurred in the past five years. This means we can capture people who were in modern slavery in that period but have since exited the situation. To elaborate, local teams of interviewers in each survey country select households based on a sampling strategy and approach that household to invite them to participate in the survey. After obtaining consent, a selected household member is interviewed about their experiences of forced labour and forced marriage that occurred in the preceding five years. They are also asked about the experiences of their immediate family members. Nonetheless, people in modern slavery are a hard-to-reach population and even though representative surveys are the current gold standard approach to produce national estimates of modern slavery, we know our estimates are likely to underrepresent the size of the issue. This is why we can confidently state these estimates are conservative.

What is the difference between the TIP report and GSI?

There are similarities in what the Global Slavery Index and the Trafficking in Persons report rate in terms of government action, however, the strength of the Global Slavery Index assessment lies in the transparency of our sources for the rating, the independence ), and a framework broader than human trafficking.

Why do you only assess 160 countries (176 for government response)?

The Global Slavery Index does not include countries with very small populations of less than a million people, nor those affected by severe conflict, due to issues of data availability and access. It also does not make sense to assess government response in countries where conflict has seen extreme disruption to government.

Is exploitation of children included?

Yes, we include children in our estimates of forced labour exploitation, including commercial sexual exploitation of children, state-imposed forced labour, and forced marriage. While we do capture some experiences of children in our surveys, we know that they are underrepresented. We also know that because sexual exploitation is difficult to capture through surveys, we identify fewer cases of children who experience commercial sexual exploitation. For this reason, we use the International Organization for Migration database of identified victims of human trafficking in combination with our surveys to produce our estimates of commercial sexual exploitation of children and adults.

Why do you define forced sexual exploitation and commercial sexual exploitation of children as forced labour?

We define forced labour in line with the International Labour Organization which includes forced commercial sexual exploitation. According to the International Labour Organization Forced Labour Convention, 1930 (No.29), forced labour is “all work or service which is exacted from any person under the threat of a penalty and for which the person has not offered himself or herself voluntarily.” Defining forced commercial sexual exploitation in this way also helps us to operationalise modern slavery in surveys.

How does child labour fit within the concept of modern slavery?

For measurement purposes, forms of modern slavery pertaining to children include the following worst forms of child labour as defined in the ILO Worst Forms of Child Labour Convention, 1999 (No. 182):

  1. all forms of slavery or practices similar to slavery, such as the sale and trafficking of children, debt bondage and serfdom, forced or compulsory labour (including recruitment of child soldiers);
  2. the use, procuring or offering of a child for prostitution, for the production of pornography or for pornographic performances;
  3. the use, procuring or offering of a child for illicit activities, in particular for the production and trafficking of drugs as defined in relevant international treaties.

Whereas the term ‘child labour’ captures child employment much more broadly, which is mainly indicated by the age of the working child.

Which countries were surveyed?

Except for Haiti, all countries included in the dataset underpinning the 2018 edition were resurveyed for the current edition. An additional 20 countries were surveyed. Overall, just under 30% of surveys were in Europe and Central Asia, approximately a quarter were in the Africa region and Asia and the Pacific each, just under 20% were in the Americas and about 10% were in the Arab States.

How were the state-imposed forced labour estimates calculated?

Information and data from the ILO Committee of Experts on the Application of Conventions and Recommendations and publicly available data and information produced by non-government organisations, international organisations, and academic institutions were used to calculate estimates of state-imposed forced labour.

Can you compare the new estimates of modern slavery to those presented in previous editions?

Walk Free has been conducting nationally representative surveys since 2014 which form the core of our approach to measuring prevalence of modern slavery. Our methodology has evolved significantly over the years due to the differences in scope and expanded data sources. Therefore, our prevalence numbers are not comparable between 2014 and 2018.

While the methodology for producing the national estimates in 2018 and 2023 remains largely the same, there are some notable differences which impact comparability:

  • Since the regional estimates presented in the Global Estimates of Modern Slavery form the starting point for calculating the national estimates in the Global Slavery Index, the following changes to the Global Estimates methodology impact comparability:
    • For the most recent edition of the Global Estimates, surveys were conducted in a larger number of countries, including in regions where there was previously a data gap.
    • An imputation model with covariates for region and international migrant population was adopted to create estimates for countries in which national surveys were not conducted.
  • Some surveys were conducted after the emergence of COVID-19, which shifted the face-to-face mode of data collection that was used for all pre-pandemic surveys, to conducting the surveys via telephone. While measures were taken to minimise and assess mode effects, this may have impacted the comparability of the prevalence estimates.
  • Multiple Systems Estimation was used in 2018 to adjust the estimates in the United Kingdom and the Netherlands. These adjustments were not made in 2023.
  • In 2023, an additional adjustment was made to countries in the Arab States region to account for heightened risk experienced by migrants unlikely to be accessed through surveys. Our national surveys of returned migrant workers in six origin countries across Asia and Africa inform the adjustments for the Arab States.

Solutions to end modern slavery

How do we end modern slavery by 2030?

It is not a question of not knowing what to do. There is a substantial and growing body of policy and programming expertise in addressing modern slavery, offering critical guidance for the future. The overall rise in modern slavery also masks numerous contexts that have registered significant reductions, offering additional key insights into the policy choices needed for progress. International legal instruments provide the normative framework for efforts against modern slavery. While everyone has a part to play in eradicating modern slavery, governments play a key role and must lead the road to eradication by:

  1. Support survivors of modern slavery to exit and remain out of slavery
  2. Establish effective criminal justice mechanisms to prevent modern slavery
  3. Develop coordination mechanisms at the national and regional level
  4. Address risk factors such as attitudes, social systems, and institutions that enable modern slavery
  5. Stop sourcing goods and services produced by forced labour

At the global level:

  • Governments and the international community must recognise and respond to modern slavery as an intersectional issue by embedding anti-slavery responses in humanitarian responses, developing social protection and safety nets, and ensuring human rights are embedded in climate change responses.
  • Governments must also focus on prevention and protection for those already vulnerable, including providing primary education to children and especially girls, and repealing hostile legislation that increases vulnerability of migrants.
  • Governments must ensure effective civil and criminal protections in legislation to tackle forced and child marriage. This includes raising the age of marriage to 18 and providing trauma-informed protection measures for those affected.
  • Governments must implement stronger measures to combat forced labour in public and private supply chains, including mandatory human rights due diligence, import controls for goods at risk of being produced by forced labour, and extending labour rights to all groups, including migrant workers.
  • Governments and businesses must prioritise human rights when engaging with repressive regimes, including conducting due diligence to ensure that any trade, business, or investment is not contributing to or benefitting from state-imposed forced labour, including where it occurs in the Xinjiang Uyghur Autonomous Region of China. Where links to state-imposed forced labour are identified, and operating in line with the UN Guiding Principles has become impossible, withdraw from sourcing goods and services. Ensure survivors of state-imposed forced labour have access to remediation, which may include financial compensation and access to legal, health, and psychosocial services.
What does Walk Free advise that wealthy/G20 governments do?

Forced labour occurs in all countries regardless of income, with the majority occurring in lower-middle and upper-middle income countries. It is deeply connected to demand from higher-income countries. The purchasing practices of wealthier governments and businesses fuel exploitation in lower-income countries, which are often at the lower tiers of global supply chains.

Wealthier governments, including the G20 must implement stronger measures to combat forced labour in public and private supply chains. This includes:

  • Introducing mandatory human rights due diligence to stop governments and businesses from sourcing goods or services linked to modern slavery.
  • Extending labour laws and fundamental labour rights to all groups without exception, including freedom of association and collective bargaining.
  • Extending social protection to all workers and provide remedy for modern slavery survivors.
  • Introducing and enforcing laws to prohibit charging of recruitment fees to employees, register and monitor recruitment agencies for deceptive practices, and ensure contracts are made available in a language migrants can understand.
What does Walk Free advise companies do to combat modern slavery?

Business and investors have both a moral and legal obligation to protect workers and combat forced labour in their supply chains. Walk Free works with business and the financial sector to combat forced labour, focusing on supply chain transparency, due diligence, ethical recruitment, and worker protection and redress.

Through our Business and Investor Toolkit, Walk Free provides a library of research, tools and guidance to support companies.

What does Walk Free advise citizens do to combat modern slavery?
  • Get informed: Learn about modern slavery and its core drivers.
  • Champion accountability at school, university, work, with your government.
  • Demand transparency: as a consumer, you have more power than you realise.
  • Support the frontline: donate to existing initiatives, projects, or organisations, particularly those which are community or survivor led.

Find out how to get involved in the global movement to address modern slavery.

Walk Free

What exactly does Walk Free do to reduce modern slavery?

Walk Free are the creators of the Global Slavery Index, the world’s most comprehensive data set on modern slavery. We use this data to mobilise powerful forces for change against these human rights abuses. We work with governments and regulators, businesses and investors, and faith and community leaders to drive systems change and we partner directly with frontline organisations to impact the lives of those vulnerable to modern slavery. We work with survivors to build the movement to end modern slavery, recognising that lived experience is expertise and survivors are central to identifying lasting solutions. Walk Free’s international team includes statisticians, criminologists, lawyers, and international development experts, working to create and agitate for mass systems change to address the root causes of modern slavery. Find out more about what we do.

Using Walk Free’s data

Can I republish/redistribute data from the GSI?

Data that are produced through the Global Slavery Index are all made available under the Global Slavery Index Terms and Conditions. Specifically, where a party seeks to download Global Slavery Index data, they agree to the terms and conditions of the Global Slavery Index Data Use Licence.

Under the Data Use Licence, Walk Free grants Licensees a worldwide, royalty-free, non-exclusive, licence to exercise certain rights indefinitely, with certain restrictions.