Dear Jon 

National Referral Mechanism and Duty to Notify statistics 

We recently completed our compliance check of your National Referral Mechanism (NRM) and Duty to Notify statistics against the Code of Practice for Statistics. We carried out a complementary compliance check of the Office for National Statistics’ (ONS) Modern slavery in the UK and Child victims of modern slavery in the UK compendium articles, to help us understand the modern slavery data landscape and how the National Referral Mechanism (NRM) statistics fit into this landscape. 

Modern slavery is a term for all forms of human trafficking, slavery, servitude and forced labour. Measuring the prevalence of modern slavery is challenging because there is no single source or method that can accurately quantify the number of victims. The NRM currently provides the best available estimate of the number of potential victims in the UK. It is therefore a highly valuable data source on modern slavery. Potential victims that come to the attention of authorised ‘first responder’ organisations are referred to the NRM. NRM figures are known to be an undercount because many cases of modern slavery remain hidden or unreported.   

We found a range of positive features that demonstrate the value and quality of the statistics: 

  • Since taking over production of the NRM statistics from the National Crime Agency in 2019, Home Office has improved the presentation and accessibility of the statistics, for example, by adding commentary to the statistical bulletin and releasing the data tables in a reusable format. Information has been added on different aspects of the NRM process, such as the number of ‘conclusive grounds’ decisions, which adds insight on the proportion of referrals deemed by Home Office to be genuine cases of modern slavery. A user told us that they value the data on the Duty to Notify process, which was added to the bulletin in 2021. It is good that the statistics team has used internal and external peer review to drive improvements.  
  • The users we spoke to, and the letter we received from academic and sector users of modern slavery data, highlighted the importance of, and need for, more data on key areas of modern slavery, including immigration outcomes, criminal justice outcomes and support access. We therefore welcome the work your team is doing to link NRM data with immigration data. Data linkage is the only way to fill certain information gaps on modern slavery and immigration, such as the number of modern slavery victims that have applied for asylum, and the number of people coming to the UK via different routes. To maximise the value of the NRM data and generate further insight, we encourage your team to be ambitious in its data linkage plans, by exploring opportunities to link NRM data with a range of other data sources.  
  • The statistical bulletin is transparent about methods changes, such as the 2019 change to the recording of exploitation types. A caveat about the lack of comparability with previous data gives helpful advice to users. Making the caveat more prominent would further support appropriate use of the statistics.  
  • It is good that anonymised disaggregated NRM data are freely available to academic researchers through the UK Data Service. Home Office has also given some non-governmental organisations and members of the public access to the anonymised data. 

We also identified several ways in which the value and quality of the statistics could be enhanced: 

  • The insight of the statistical bulletin could be improved by adding a clearer narrative of victims’ journey through the NRM process. To help users visualise and better understand the NRM process, we encourage you to add a flow chart like the one in ONS’s Modern slavery in the UK article. While it is good that the bulletin discusses possible drivers of changes in the number NRM referrals over time, it should acknowledge that recent increases in the number of referrals may reflect changes in awareness and identification of potential victims by ‘first responder’ organisations, as argued in the ONS article. It should also explain why the NRM and Duty to Notify figures are likely to be undercounts, and that the true number of modern slavery victims may be higher.  
  • The statistics are not granular enough to meet some users’ needs. The users we spoke to said that they would welcome further breakdowns of the NRM referral data in the bulletin and data tables, including breakdowns by exploitation sub-type, age of victims, and location of exploitation. They also told us they would like to see outcome decisions broken down by UK and non-UK nationals. Expanding the datasets released via the UK Data Service would enhance their value too. We recommend that you engage directly with users to understand their needs regarding the release and presentation of the statistics. 
  • We heard about the challenges that academic users have faced in terms of permissions and access required for research involving the NRM. Difficulties with accessing modern slavery data were also highlighted by the former Independent Anti-Slavery Commissioner in her Annual Report 2021-2022. Improving data access for research would support better public understanding of modern slavery and allow greater scrutiny of the response to modern slavery. 
  • The bulletin contains limited information about the quality of the statistics. To assure users about the quality of data and data standards, and aid interpretation of the statistics, the quality and methods information should be significantly expanded. The information should cover the NRM live management information system, how data are recorded, the system’s strengths and limitations, and sources of bias in the data. It should discuss data accuracy and reliability, comparability and coherence, and other aspects of data quality. Given the variety of authorised ‘first responder’ organisations referring potential victims and sharing data, it should also explain how data are quality assured at all stages of the data collection and statistics production process. Our Quality Assurance of Administrative Data (QAAD) framework might be helpful for reviewing and reporting quality. 
  • The bulletin states that the statistics may differ from those in previous or future bulletins, due to updates to case files on the live management information system. The scale, nature and impact of revisions should be explained, to assure users about the consistency and comparability of the statistics.  
  • Modern slavery is a relatively data-rich area, as evidenced by ONS’s modern slavery in the UK compendium article. The NRM bulletin should signpost other data sources on modern slavery to help users easily find related statistics.  

Lastly, it is important that the integrity and credibility of the NRM statistics are not undermined. In a recent letter to Professor Jennifer Rubin, we highlighted the need for clarity and transparency around the evidence used to support public statements about modern slavery. We welcome the commitment in Professor Rubin’s response to ensuring that public statements are sourced from published statistics or other reliable evidence. 

Thank you to your team for its positive engagement during this review. We look forward to continuing to engage with your team. Please get in touch if you would like to discuss any aspects of this letter further or if we can offer further assistance as these statistics continue to develop. 

I am copying this letter to Tom Bucke, Head of Unit for Drugs, Exploitation and Abuse Analysis at Home Office; John Marais, Deputy Director Crime, Income and Wealth Division at ONS; and Meghan Elkin and Peter Jones, heads of the Centre for Crime and Justice at ONS. 

Yours sincerely 

Mark Pont 

Assessment Programme Lead 


Related Links:

Mark Pont to John Marais: Statistics on modern slavery in the UK (March 2023)

Maya Esslemont and Anna Powell-Smith to Ed Humpherson: Modern slavery data (October 2022)

Ed Humpherson to Jennifer Rubin: use of National Referral Mechanism statistics (December 2022)

Jennifer Rubin to Ed Humpherson: use of National Referral Mechanism statistics (January 2023)