March 18, 2021

Updated Evidence and Gap Map on Implementation

Centre for Homelessness Impact

Until 2018 there were no reliable tools to help us identify what we did and didn't know about homelessness interventions, where our understanding could be strengthened and where there were still gaps to be filled. Evidence was scattered around in different databases, journals, websites and grey literature, and there was no way for decision-makers to get a quick overview of the evidence base as a whole. 

When CHI launched in 2018, our first priority was to address this need. We immediately began working with our partners at the Campbell Collaboration and Heriot-Watt University to systematically map all of the relevant evidence on homelessness interventions from across the globe via two Evidence and Gap Maps (EGMs).

Watch our video on EGMs

Today marks the second update of our implementation map, which maps out the available evidence across key issues relating to the implementation of homelessness interventions. The map can guide users to relevant evidence, visualising where more research is needed or can be synthesised. This helps commissioners of research target research investments faster and in a more strategic, impactful way.

What has changed since the previous edition?

The 2021 edition added 63 studies to the map. It also excluded 34 studies after rescreening, mostly because those studies were impact evaluations which had insufficient implementation evidence to be included. The 2021 edition therefore hosts 275 studies whereas the 2018 edition hosted 246 studies.

The majority of studies in the Implementation Map come from North America, with 104 studies from the United States and 38 from Canada. Although a minority of studies in the Implementation Map are from the UK (73 = 27%), UK research represents a far smaller proportion of the whole in CHI’s Effectiveness Map (26 = 6.5%), highlighting that the nation has a stronger tradition of qualitative homelessness research than it does of quantitative. The majority of the studies in the map (217 = 78%) were published after 2010. Prior to 2014, around 10 studies were published annually, after which there was a sharp increase with 25-30 studies published annually up until 2019. This is good news, as we have also reported a rapid increase in the number of studies conducted each year for inclusion in our Effectiveness EGM.

The EGM shows that there is a lack of research into the impact of financing, employment, legislation and communication on implementation of interventions. 'Services and outreach' and 'accommodation based' interventions are sufficiently plentiful to synthesise existing evidence.

Read the report

Why is this update important?

We know that much of the money spent on homelessness is going towards interventions that have not been rigorously evaluated,meaning we can’t say if they truly work. If we are to invest wisely in homelessness prevention, it is crucial that money is spent in the right places, and in the right way.

Our hope is that the homelessness field can reflect on the findings presented in the maps and continue improving evidence on homelessness, but most importantly to embed reliable evidence and data into all of our decision-making processes and structures. 

Try the map

What are our next steps?

The Centre is using the EGMs to identify key areas where we lack relevant evidence. This helps us address some of the gaps by commissioning new trials. Likewise, where there is sufficient evidence in the EGMs, we aim to synthesise existing bodies of evidence through commissioning systematic reviews and adding content to it’s other online tools (see CHI’s Intervention Tool and Evidence Finder). 

The maps are updated annually so the EGMs will capture new developments in the field. The gaps in the Implementation EGM highlight that researchers and commissioners should evaluate the impact of financing, employment, legislation and communication on implementation of interventions. There is sufficient evidence for synthesis in 'services and outreach' and 'accommodation based' interventions. 

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