A new scoping review by the Rights Lab at the University of Nottingham has highlighted the urgent need for scientifically rigorous and regularly updated estimates of modern slavery prevalence in the UK.
Modern slavery victims and survivors are a seldom heard, often hidden population. There have been five prevalence estimates carried out since 2014, but there is still currently no national consensus on the number of modern slavery victims and survivors in the UK, because estimates have a high degree of variation and methodological challenges.
Robust prevalence estimates are critical for effective policy development, resource allocation, and survivor support. Without accurate data, policymakers, law enforcement, and frontline services cannot fully understand the scale, distribution, or evolving nature of modern slavery in the UK.
This scoping review, led by Professor Todd Landman, Rights Lab Research Director and Professor of Political Science – and funded by the UK Independent Anti-Slavery Commissioner and the Institute for Policy and Engagement at the University of Nottingham – examines all the possible methods for estimating prevalence, and advocates for a revised UK prevalence estimate to be undertaken.
Currently, the UK lacks a national consensus on the number of victims, with previous estimates ranging widely from 8,300 to 136,000. This variation, combined with the broadening definition of modern slavery under the Modern Slavery Act (2015), has underscored the need for more reliable approaches to measuring prevalence.
The Key findings from the review, conducted between November 2024 and July 2025, found:
- Multiple Systems Estimation (MSE), using data from the National Referral Mechanism and Local Authorities, is identified as the most cost-efficient and least-biased method for estimating prevalence at the national level.
- Surveys and targeted sampling strategies remain important tools for estimating prevalence of specific forms of modern slavery within subpopulations.
- The UK has a well-developed but fragmented data infrastructure that, if better integrated, could provide unprecedented insights into prevalence, risk, and vulnerability.
- Advanced techniques such as machine learning, artificial intelligence, and geospatial analytics present untapped opportunities to extend understanding beyond prevalence to include risk mapping and vulnerability modelling.
The findings recommend that a modern slavery and human trafficking data warehouse be established as part of the UK’s National Data Library to enable inter-agency data sharing, along with the development of modern slavery risk maps to inform prevention, law enforcement and survivor support.
Eleanor Lyons, the Independent Anti-Slavery Commissioner, added: “It’s vital that we can identify and support victims of modern slavery across the country. Behind every number is a person whose freedom has been taken away. Good data is the foundation of good policy. That’s why it’s important we establish a reliable national estimate of modern slavery prevalence, so we are able to direct resources effectively, strengthen prevention, and ensure victims and survivors are seen and supported. This review is an important step towards developing a clear, evidence-based picture of modern slavery in the UK.”
