Mind the Gap(s)? Evidence and UK Policymaking on Human Trafficking and Modern Slavery

ABSTRACT This article examines four critical gaps in the evidence-policy relationship on human trafficking and modern slavery (HTMS) in the UK: prioritization, epistemology, synchronization and trust. Drawing on multiple sources, the authors outline key features of the landscape around evidence and policy in the UK, identify ways to address gaps and bring together researchers, those directly affected, and policymakers. The findings point to a growing consensus on improving research on HTMS, but a continuing need for work to provide appropriate conditions for a productive evidence-policy system. The conclusions reflect opportunities and challenges in the light of recent political moves in the UK that undermine linkages between evidence and policy.


Introduction
There is now a substantial and growing amount of research on human trafficking and modern slavery (HTMS), despite it being a comparatively new field of inquiry.Yet there remain concerns about the effectiveness of policies (McDonald, 2014) and the quality and methodological rigor of evaluations of HTMS policies and programs, even if they may be improving (Bryant & Landman, 2020).The UK government has been repeatedly urged to improve the evidence base for its activities in this area (e.g., (Commonwealth Parliamentary Association [CPA], 2018; Independent Commission for Aid Impact [ICAI], 2020), and policy development has been described by scholars as non-rational, "running ahead of research" (Broad & Turnbull, 2019).
Focusing on the UK as a case study, the article identifies and examines four critical gaps or differences -around prioritization, epistemology, synchronization, and trust.We reflect in each case on opportunities and challenges for developing a more productive relationship between research and policy.
The role of evidence in UK policymaking on HTMS came to the fore in 2022 and 2023 concerning two pieces of legislation: the Nationality and Borders Act 2022 and the Illegal Migration Bill (introduced in March 2023).Both aimed to address the UK Government's claims that the modern slavery system is being "abused" by individuals claiming to be victims to avoid deportation and to secure their immigration status.Yet these claims have been widely criticized as "unevidenced" by civil society and described as "counter to all evidence" by scholars. 1They pointed out that the government's research (Home Office Analysis & Insight [HOAI], 2020) concluded that deterrence does not work and worsens the risks of exploitation and forced labor. 2 The UK's statistics regulator has also raised concerns about the improper use of statistics on modern slavery by the Home Secretary (Humpherson, 2022).
Analysis of the UK's policy development in this area suggests a limited role for research and evidence, pointing to the importance of path dependency and embedded organizational interests of immigration and criminal enforcement agencies (Balch & Geddes, 2011).Some academics have criticized the policy as being driven not by evidence but by ideology, racism and misogyny (O'Connell Davidson, 2015), or following a securitized and politicized logic (Broad & Turnbull, 2019).Meanwhile, international scholarship on HTMS frequently features complaints about data availability 3 4 and quality and conceptual confusion over definitions (Loff & Sanghera, 2004).
This sits somewhat at odds with the growing number of international initiatives and programs, often government-funded, which are specifically designed to improve the use of evidence on HTMS, e.g., the Delta 8.7 knowledge platform of Alliance 8.7, 5 the Human Trafficking Research Initiative 6 and Monitoring to Evaluation of Trafficking in Persons (METIP). 7In the UK, those who deliver or scrutinize policy on HTMS have published their priorities for research and evidence (e.g., see Independent Anti-Slavery Commissioner [IASC] research priorities 8 ), notably, the UK Annual Report on Modern Slavery 2018, produced by the UK Government and devolved administrations, which included an annex on research priorities.Academics in the UK are increasingly encouraged to pursue impact for their research through the Research Evaluation Framework (REF), by developing what are called 'impact case studies' which describe how their research has made a difference.In the 2014 REF there were 21 impact case studies submitted that mentioned "human trafficking" OR "modern slavery", and in the 2021 REF this had more than doubled to 48 cases. 9 Why do problems of evidence usage continue to affect this area, and what can be done to address them?As part of the Modern Slavery and Human Rights Policy and Evidence Centre (MS-PEC), launched in 2019 based in the UK and dedicated to improving the evidence-policy relationship in this area, the authors are well-placed to answer these questions.The MS-PEC is a £10 m investment funded through the UK Research and Innovation (UKRI) Strategic Priorities Fund (SPF) through the Arts and Humanities Research Council with the support of the Economic and Social Research Council.As with similar centers, the MS-PEC aims to improve the use of evidence in policymaking but has some unique characteristics around collaboration, co-production, and human rights.Its Strategic Delivery Plan explained its mission as bringing together "academics, policymakers, businesses, civil society, survivors, and the public on a scale not seen before in the UK to collaborate on solving this global challenge.The Modern Slavery PEC's approach is rooted in human rights" (MS-PEC, 2021, p. 3).
The authors help lead the MS-PEC.One is the Director of Research at the MS-PEC and a professor of politics at the University of Liverpool, and the other is the Director of Policy Impact at the MS-PEC and has worked in government social research and policy advisor roles in the UK civil service.In the rest of this article, we draw on multiple sources, including relevant literature, narrative "impact case studies" on modern slavery and human trafficking from the UK's Research Evaluation Framework exercise (which took place in 2014 and 2021), a consultation on research priorities on modern slavery carried out by the MS-PEC in 2020, and our own experiences of engaging with policymakers on research, and funding and managing multiple research projects. 10 We are interested in the evidence-policy system, the gaps and differences, why they persist, and what works to develop a more productive relationship.Sometimes, accounts of how evidence usage works can risk descending into an exchange of "slogans" between policymakers and critical scholars (Cairney, 2021).On the one side, there is the accusation that evidence is 'cherry-picked' by politicians to support dubious claims and to further a particular political approach (Thomas, 2022).While the concept of "evidence-based policymaking" (EBPM) is often criticized as betraying an overly positivist, empiricist understanding of the world, assuming research can produce reliable answers or that difficult "ethical and moral issues faced by policymakers can be reduced to questions of 'best evidence'" (Greenhalgh & Russell, 2009).We seek to develop a more constructive approach, identifying why and where the critical gaps or areas of difference are between the researcher and policymaker communities and developing new ways for these to be more effectively bridged.Before turning to this, it is helpful to provide some context on the UK's development of policies to address HTMS, because norms and practices around evidence usage in decision-making are embedded, as observed during the COVID-19 pandemic (Hadorn et al., 2022).

Context: From Palermo to the UK's Modern Slavery Act
The HTMS policy field is relatively new, traced to an international agreement on a definition of human trafficking at Palermo in 2000 (UN, 2000).This agreement included one mention of research (Art 9: 2) and encouraged "information exchange and learning" (Art 10) but, in general, established a quite prescriptive framework for how states should address the issue, referred to as the 3 P's: prosecution, protection, and prevention.States like the UK have scope to determine their path to interpret, prioritize and integrate Palermo with existing policies.The UK's policy response, currently framed by the Modern Slavery Act ( 2015), sees the Palermo definition of human trafficking as one form of modern slavery, used as an umbrella term and including other types of exploitation, such as forced labor in business supply chains.There are multiple intersections and overlaps with other types of exploitation, leading to competition at the international level around appropriate terminology and policy responses (Chuang, 2014).
Implementation is also mediated via regional forms of governance.In the European context, this means additional agreements and instruments on human trafficking through the European Union (EU) and Council of Europe (CoE), both with elements of evidence and expertise.Notably, the European Convention on Action against Trafficking in human beings (ECAT) 11 included the creation of Group of Experts on Action against Trafficking in Human Beings (GRETA), an international "multidisciplinary" team that evaluates signatories every four years.The 2011 EU directive requires, among other things, the creation of national/special rapporteurs with a role that includes connecting evidence with policy, through scrutinizing policies, assessing trends, co-operating with other organizations and reporting. 12Although the UK left the EU on 31 January 2020, it remained part of the Council of Europe and had already set up (from 2014) a similar position in the Independent Anti-Slavery Commissioner (IASC) to encourage best practice, which explicitly included the duty to "undertake or support the carrying out of research" (IASC, 2022, p. 46). 13 In the UK, responsibility for HTMS sits with the Home Office, which has its tradition of carrying out and commissioning research, predominantly on crime and criminal justice issues.Capacity has grown significantly in the last 20 years with the growing number of researchers and analysts re-10 At the time of writing, the Modern Slavery PEC had funded teams comprising 89 academic team members from over 35 universities and academic institutions, 26 individuals from 17 NGOs, four private sector organizations several other governmental and international organizations, and independent parties.organized under Science, Technology, Analysis, Research and Strategy (STARS) in 2020, which acts as "a strategic center that informs, drives, coheres and connects the delivery of the Home Office priorities across government and beyond." 14Home Office Analysis and Insight, a Directorate within STARS, has more than 350 analysts. 15Finally, it should be noted that this policy area is not only the responsibility of Westminster.The UK's devolved administrations have developed their own legislation and strategies, with some distinctions from the UK Government.For example, the Scottish Government uses the terminology "human trafficking and exploitation" in its legislation and strategy. 16

Evidence and UK Policy on HTMS: 4 Key Gaps
What are the critical gaps and differences around evidence and policy on HTMS in the UK?The following analysis is based primarily on three key sources: 1) a consultation into research priorities on modern slavery carried out between July and October 2020, including a short survey with 121 respondents and eight roundtables with experts and stakeholders (Balch, 2021); 2) analysis of impact case studies submitted in 2014 and 2021 to the UK's Research Evaluation Framework, where narrative examples of impact relating to research are submitted by UK academic institutions and published; and 3) internal monitoring and evaluation of the work and impact of the Modern Slavery PEC.

Prioritization
There are several differences between stakeholders on the priorities for research into HTMS.This is not simply researchers versus policymakers; stakeholders in research include civil society and nongovernment organizations (NGOs) that play an essential role in delivering services and, perhaps most importantly, those directly affected.The consultation on research priorities by MS-PEC (Balch, 2021) identified some differences between these groups and areas of overlap and consensus.While policymakers strongly preferred research on the effectiveness of different interventions ("what works"), academics were keen to prioritize social justice and equity.NGOs (and some academics) championed equality, diversity, and inclusion (EDI) issues in research.There was, however, evidence of a consensus on prioritizing the meaningful inclusion of people with lived experience in research.In terms of different research areas, academics were more likely to say they prioritized research into "modern slavery in supply chains" and less likely to say they prioritized "preventing modern slavery" or "understanding survivor needs and enhancing victim support" when compared with non-academic respondents (Balch, 2021, p. 16).
Evidence from the 2014 and 2021 REF case studies indicates a growing body of academic work but also reveals quite specific approaches and priorities concerning impact.In both evaluations, researchers were less involved in strategic policy development and more focused on exerting influence via expert scrutiny.In 2014, there was more research helping develop support services or treatments for "at-risk" populations by relevant organizations, particularly NGOs, and research on the consequences of policy and services for groups such as sex workers, but the focus of this research was very geographically spread with relatively few projects specifically on the UK.In 2021, considerably more case studies appeared on supply chains.As of 2014, a key theme in terms of the type of impact was influenced through improving understanding/awareness of the problem itself or producing research that improves scrutiny of existing approaches because relatively fewer case studies claimed to have influenced UK governments' anti-trafficking policy development strategically.There may be several reasons for this, not least that the positive impacts of research directly helping those affected can be 14 https://www.gov.uk/government/publications/home-office-annual-report-and-accounts-2020-to-2021 15 A call for academics to present research findings in 2018 noted that HOA&I employs "more than 350 analysts" https://wrdtp.ac.uk/ exciting-opportunity-at-the-home-office/ directly observable but could also indicate the importance of the other gaps highlighted here (e.g., synchronization, epistemology, trust) impacting the relationship between policymakers and researchers in this area.
In addition to consulting on research priorities across the sector, the MS-PEC has sought to navigate and bridge gaps in research priorities between those creating the "demand" for policyoriented research and those who "supply" research.The MS-PEC regularly engages with policy officials working on modern slavery to understand their ongoing priorities for evidence.We have found that policymakers' needs for evidence often fall into two broad categories: "evergreen" or "responsive".The former refers to strategic areas of interest, such as what works and for whom in addressing HTMS, while the latter refers to more narrow and specific needs for evidence, such as how a specific policy is working in practice or the nature of a particular issue.The MS-PEC has designed various research funding and commissioning models that enable funding of a portfolio of longer-term projects that address "evergreen" policy priorities and more agile and focused projects that address "responsive" evidence gaps.The MS-PEC funds most of its research through open funding calls that set the objectives for research in consultation with policymakers and people with lived experience to increase the research projects' relevance.Throughout research projects, the MS-PEC is "hands-on" with funded research teams, supporting projects to maximize their policy impact.

Epistemology
When working with researchers, practitioners, and policymakers, the different understandings of the nuances, strengths, and weaknesses of different types of knowledge and knowledge production can be quite noticeable.Differences remain over perceptions of the meaning/value of (or problems with) the terms "modern slavery" and "human trafficking," and around the causal understandings of the phenomena and linkages with other policy issues and agendas.As mentioned earlier, there is one area of growing consensus: the value of lived experience as an important type of evidence and expertise.However, more work is needed to integrate this into the evidence-policy system and establish the appropriate standards for research that meaningfully engages and includes people with lived experience to avoid it being unethical and tokenistic (Asquith et al., 2022).
Different preferences exist over methodological approaches (qualitative vs quantitative), but these link to different understandings of the strengths and weaknesses of such approaches, sampling techniques, etc. and the extent to which findings can support recommendations or courses of action.The MS-PEC has developed new ways to communicate these complexities to policymakers but also works intensively with funded research teams, encouraging them to establish clear linkages between findings and recommendations and to explain the relative strengths and limitations of methods and findings in written and verbal briefings to policymakers.
One assumption is that policymakers prefer "hard data," economic modeling, cost-benefit analysis or randomized control trial (RCT) and are skeptical of any work with a more humanities-type approach.For issues like HTMS, it may not always be possible or ethical to carry out RCTs to accurately determine the effectiveness of different interventions.These kinds of approaches to evidence may even be at odds with scholarship on social issues, where problems are usually understood to be complex, systemic, or "wicked" (Eden & Wagstaff, 2021).There is undoubtedly greater demand from policymakers for "hard" social science, and while there is a sub-set of researchers working on prevalence methodologies and quasi-experimental studies, research in this area is generally dominated by qualitative approaches.This could be for several reasons, not least because this type of research can have lower costs; the short history of research in the area also means that measures and indicators are relatively new, not standardized or still being developed, so quantitative techniques are not yet viable.Our consultation on research priorities also revealed a desire for researchers and civil society to focus on a deeper understanding of the phenomena itself and foreground the experiences of those affected and the role of context, all conducive to qualitative approaches from the arts and humanities.
Notwithstanding this, we have found policymakers open to the merits of qualitative and small-sample studies.Moreover, their interest in more and "better" data to inform decisions on HTMS is shared by other research stakeholders.It is just that this means different things to different groups -depending on what that data is, who collects and holds it, what analysis/ research can be carried out with it, and for what purpose.There are well-documented challenges around the ethics of data, but also more practical obstacles to achieving the potential of data science approaches, including the difficulties of sharing data between government, nongovernment organizations, and research teams.Preparing data for research can be costly, and an understandably cautious approach when data relates to criminal and traumatic experiences means the barriers to sharing are high.

Synchronization
One of the biggest challenges to bridge for those working on the evidence-policy system is the gap between the timing for policymakers who need research to inform decisions, and the timescales required to carry out that research, especially if it is to be done equitably, inclusively, and to involve lived experience.It is often assumed that policymakers need evidence as quickly as possible, and this is often true, but there are also the longer-term ("evergreen") priorities that are less time-bound.Ultimately, there are limits to synchronization: even apparently "responsive" and narrow demands for new research can be dynamic, for example, as politicians' priorities evolve.This is particularly evident when trying to insert evidence into the development of legislation, where Bills are frequently amended as they pass through Parliament.
The MS-PEC has designed multiple research commissioning models to ensure a balanced portfolio between agile, quick turnaround research and longer-term 12-month projects.The MS-PEC's regular engagement with policy officials has also been an opportunity to maintain an open dialogue about the schedule that policymakers are working to and build policymakers' understanding of what kinds of research on HTMS are possible within different timescales.Evidence reviews assessing existing literature can be completed more quickly than survivor-involved empirical research, which requires ethical clearance processes and recruitment of a research team.The MS-PEC has increasingly drawn on the capacity and expertise of its core team members to produce highly agile syntheses of evidence, for example, to inform Parliamentary committee inquiries or to set out the evidence base on an issue via Policy Briefs.A key challenge remains for responsive research and rapid reviews to meaningfully include or be led by those with lived experience.

Trust
Developing trusted and resilient relationships between policymakers and those involved in producing research is central to addressing all the gaps and differences outlined above.The results of the MS-PEC consultation showed that the bridge-building challenge extends beyond connecting academics and officials -it highlighted the need to create a more inclusive and collaborative space to enhance the quality and potential impact of research.
Researcher (dis)engagement with the Home Office is tied up with political differences and previous experience, e.g., criminologists calling for a boycott based on how their work had been used (Walters, 2008).Conventional wisdom is that most academics ideologically oppose Home Office priorities, particularly on immigration (Van de Werfhorst, 2020).Added to this is the growing willingness of some prominent UK politicians to denigrate experts and expertise, which creates a challenging backdrop to productive engagement (Norris & Inglehart, 2019).Even more complicated is bringing together policymakers with survivors who have had negative experiences with other Home Office officials working in immigration and asylum.
The MS-PEC's core organizational values of independence and transparency17 have established a clear position in the research-policy ecosystem, which is impartial and nonpartisan.The MS-PEC has sought to act as a convenor, bringing together different groups working to understand and address HTMS that may not typically interact and to maintain an ongoing dialogue with and between policymakers and researchers.
There are practical issues which are more easily bridged.Our experience suggests that, on the one hand, researchers are unaware of both the policy processes in the areas they are conducting research, and the level of expertise officials may have in their field.On the other hand, officials can find some academic work inaccessible and difficult to filter and identify relevant findings from the rapidly growing pool of gray literature.
Since its launch in 2019, the MS-PEC has developed different strands of ongoing engagement with stakeholders in research and policy on HTMS.In 2022, more than 80 meetings were conducted with policymakers and stakeholders and encompassed other partnership work, including the development of platforms for collaboration.The research priorities exercise led to the funding of new research on EDI and an agenda on survivor inclusion.In practice, this means putting in place processes for equitable inclusion in research production, such as requiring applicants to demonstrate commitment to partnerships and to consider meaningful ways to involve people (e.g., as peer researchers or through advisory groups).The MS-PEC has enabled this by increasing the proportion of funding available to non-academic partners and supporting research teams to begin influencing targets right from the start of the research process.

Conclusions
There are a range of challenges and opportunities in bringing stakeholders together and improving the relationship between evidence and policy on HTMS.The evidence-policy relationship in this area is dynamic and fast-moving due to the complex and politicized nature of exploitation which is so intimately tied to structural hierarchies and inequalities.Gaps and differences thus persist across many aspects of this area, but there are signs of convergence around changing norms over "what counts" as evidence, "who counts" as an expert, and how research should be funded and carried out.This connects with a shared desire for a more ethical, equitable, and inclusive approach to research, rooted in the conviction that this is the best pathway to generating the kinds of impactful evidence to support policymakers in making better decisions.
Is it possible for a more responsive, synchronized, evidence-policy system to be built that both responds to this desire for better research but also improves how governments approach and combat HTMS?The examination of key gaps presented here suggests that some differences can be narrowed, but the objective should not be simple alignment because there is a productive tension in having greater diversity in the research field and in exposing decision-makers to new kinds of evidence and expertise.Consensus is not the point: the most potent evidence will challenge problematic assumptions about causality and disrupt systems and preferences tied to vested interests.
The risks to, and fragility of, this evidence-policy system thus becomes apparent.We saw this in the UK in 2022-2023 when a political shift suddenly and significantly widened gaps between evidence and policy on HTMS.This can appear to unravel the long-term, painstaking work to build bridges between different actors in the evidence-policy space.But it only further underlines the importance of sustaining trust and resilience in those relationships.New arguments about HTMS, however tenuous or politically inspired, require careful and rigorous scrutiny and investigation; it is through research and evidence involving those directly affected that their power with policy development can be strengthened or weakened.For entities such as the Modern Slavery and Human Rights Policy and Evidence Centre, the challenge only strengthens our resolve to develop new high-quality evidence in collaboration with those directly affected and to continue on a journey to deepen our understanding in a way that includes both researchers and policymakers.

Disclosure statement
No potential conflict of interest was reported by the author(s).

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Adopted in 2005, came into force 2008.12 EU Directive 2011/36/EU "on preventing and combating trafficking in human beings and protecting its victims."13 This position has been vacant since April 2022.