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April 7, 2022

Fourth Edition of Evidence and Gap Maps Effectiveness Report highlights encouraging growth in rigorous evidence

Dr Lígia Teixeira

Until recently, there were no reliable evidence tools to identify what we do and don’t know about ending homelessness - it was spread across databases, journals and websites, making it inaccessible to decision-makers who wanted to use evidence to improve outcomes.

To help people working in the homelessness sector easily access the evidence, we created two evidence and gap maps (EGMs). Together, these maps capture what we know about what works and why on homelessness interventions. Created in  partnership with the Campbell Collaboration the two maps capture around 600 studies on interventions – the largest resource of its kind in the world. You can watch an introductory video to our EGMs below.

The effectiveness map focuses on causal or ‘what works’ evidence such as impact evaluations or systematic reviews. When we released the first effectiveness map in 2018, we found just 221 relevant studies across the entire globe. Four years on the picture has changed significantly. The fourth edition now contains 562 studies, 112 of which were published in the past two years. 

This demonstrates encouraging growth in rigorous evidence highlighting what works to tackle homelessness. In the UK there has also been a significant increase - from 12 to 56 - but UK-based research continues to account for just 10% of the global evidence base (72% are from the USA). While the UK is publishing increasing numbers of Randomised Control Trials, only five have been published since 2016. 

This needs to change. While international studies are useful, differences in context means that approaches that worked elsewhere might work less well, or better, here. The map shows that the most critical gap in homelessness research is a lack of evidence of the cost-effectiveness of interventions, even though that type of knowledge is invaluable for policymakers trying to make the most of limited resources.

We encourage people engaged in the homelessness sector to reflect on the findings presented in the maps and join us in our efforts to improve our understanding of what works, for whom, and in what circumstances. By embedding reliable evidence and data analysis in decision-making processes, we can end homelessness for good. 

We will continue our programme of action to synthesise existing knowledge and fill gaps in the evidence, so that over time the maps come to be used as a standard reference for evidence creation and use.

We hope the report, tools and future editions will continue to make a significant contribution to the dialogue and decision-making on homelessness in years to come and lead to more strategic use of, and investment in, reliable evidence.

Read the fourth edition of our Evidence and Gap Maps Effectiveness Report

Learn more about our Evidence and Gap Maps tool

Dr Ligia Teixeira is chief executive of the Centre for Homelessness Impact

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