Report: Modern Slavery Prevalence Estimation in the UK

Evidence and data are the foundation of effective policymaking and practice in the fight against modern slavery. Yet despite considerable efforts across the anti-slavery sector including important contributions from academia, charities, and statutory bodies, significant gaps in our understanding of modern slavery in the UK remain. 

The hidden and complex nature of this crime makes it difficult to measure. But without robust and reliable prevalence estimates, our national response risks being misinformed. If we do not know how many people are being exploited, where, or in what ways, we cannot target our resources effectively, nor can we uphold our moral and legal commitments to victims and survivors. Too many remain uncounted and unsupported which is why I made the development of a stronger evidence base a central pillar of my Strategic Plan for 2024–2026. A key part of this work involves supporting and commissioning research that can shed light on the scope, scale, and nature of modern slavery. 

This scoping review by the Rights Lab represents a vital contribution to that evidence base. It provides a comprehensive and timely assessment of the methodologies available for estimating modern slavery prevalence in the UK. It critically evaluates a wide range of approaches from Multiple Systems Estimation (MSE) to survey-based methods, to emerging innovations such as Natural Language Processing (NLP), geospatial analysis, and machine learning. 

The review demonstrates clearly that while no single method will capture the full complexity of modern slavery in the UK, different methods can be applied strategically to estimate prevalence across the broad umbrella of modern slavery offences and within specific subpopulations. The report also highlights the considerable data assets we already hold in the UK, while making the case for better integration, ethical governance, and survivor-informed approaches to research.

Importantly, the review echoes and strengthens the need for the creation of a modern slavery and human trafficking data hub, a vital tool for enabling inter- agency data sharing and analysis. Such a resource could not only underpin regular prevalence estimations but also support the development of national risk maps, help identify patterns of vulnerability, and enable more targeted and effective policy responses.

Looking ahead, I will be expanding my focus to look at emerging threats by identifying and analysing trends in modern slavery across short, medium and long-term timeframes. This work will aim to provide early-warning intelligence and practical foresight tools to inform disruption strategies before patterns of harm become entrenched. The insights and methodological recommendations set out in this report will be instrumental in shaping that agenda, offering both the analytical foundations and data-driven approaches required to anticipate and address the evolving nature of modern slavery in the UK.

I urge policymakers to give serious consideration to the recommendations set out in this review and to embed them within the UK’s wider strategic response to modern slavery. Strengthening our national evidence base must be treated as a priority to enable better-targeted interventions and improved outcomes for victims and survivors. Robust prevalence estimation is not just a research ambition; it is essential to addressing the true scale and nature of exploitation in the UK both now and in prevention of future harms.

You can read the full report here.