Evidence and Gap Maps

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Search a global evidence base

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Our Evidence and Gap Maps bring together evidence on homelessness interventions from around the world to highlight where evidence does or doesn’t exist on what works and why. This helps target research investments faster and in a more strategic, impactful way.

The Effectiveness Map, or ‘what works’ map, captures impact evaluations and effectiveness reviews and it highlights the level of confidence we can have in the findings. The Implementation Issues, or ‘why things work or not’ map, focuses on the factors that impact on the successful implementation of homelessness interventions. Together the two maps capture around 1,000 studies on interventions – the largest resource of its kind in the world.

These Evidence and Gap Maps have been created with our partners at The Campbell Collaboration and Heriot-Watt University and they will be updated at regular intervals.

The Effectiveness Map

Also known as the ‘what works’ map, you can find 690 quantitative impact evaluations and effectiveness reviews of homelessness interventions. It also shows the level of confidence you can have in the findings - high, medium and low confidence. View the map’s report, take a look at its Standards of Evidence, and view the critical appraisal.

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Implementation Issues Map

Also known as the ‘why things work or not’ map, you can use it to find 407 qualitative process evaluations that examine factors which help or hinder the successful implementation of homelessness interventions. The information is currently displayed in two digital tools – barriers and facilitators. An integrated version will be available in future. Read the Implementation Issues Map Report.

Use the map

The Effectiveness Map, or ‘what works’ map, captures impact evaluations and effectiveness reviews and it highlights the level of confidence we can have in the findings. The Implementation Issues, or ‘why things work or not’ map, focuses on the factors that impact on the successful implementation of homelessness interventions. Together the two maps capture around 600 studies on interventions – the largest resource of its kind in the world.

Locate and access relevant studies on homelessness interventions

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We are always adding studies to the growing evidence base. If you know of any we have missed please let us know.

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Evidence standards

The Centre is applying standards of evidence to each of our tools and maps, which have been developed with our partners The Campbell Collaboration. 

Standards of Evidence for the Effectiveness Map

Each study in the map has been rated as high, medium or low for ‘confidence in study findings’. For systematic reviews in the map this rating was made using the revised version of ‘A MeaSurement Tool to Assess systematic Reviews’ (AMSTAR 2). The rating of primary studies was made using a critical appraisal tool based on various approaches to risk of bias assessment.
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The two tools - AMSTAR 2 and the primary study critical appraisal tool – assess a range of items regarding study design and reporting. Some of these items are designated as ‘critical’. The overall rating for the study is the lowest rating or any critical item.

Primary studies

CRITICAL ITEMs

Study design: At least 3 RCTs or 5 other studies with a combined sample size of at least 300
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Attrition: High levels of attrition, especially differential attrition between the treatment and comparison groups, reduce the confidence we can have in study findings.

Outcome measure: For the study findings to be usable and meaningful there should be a clear description of the outcome measures, preferably using existing, validated approaches.

Baseline balance: We can have less confidence in study findings if there were significant differences between the treatment and comparison groups at baseline. 

OTHER ITEMS

 (assessed but not affecting overall rating):

Blinding: The absence of blinding of participants and researchers can bias study findings. This may be so even though blinding is not possible.

Power calculations: Power calculations help determine the sample size required. Without such calculations there is a risk of underpowered studies and so a high likelihood of not correctly identifying effective programmes.

Description of intervention: A clear description of the intervention is necessary to be clear what is being evaluated, so that effectiveness is not assigned to similar, but different, interventions.

Systematic Reviews

CRITICAL ITEMs

Protocol registered before commencement of the review

Adequacy of the literature search. Justification for excluding individual studies

Risk of bias from individual studies being included in the review

Appropriateness of meta-analytical methods

Consideration of risk of bias when interpreting the results of the review

Assessment of presence and likely impact of publication bias. 

other ITEMs

PICOS in inclusion criteria

Rationale for included study designs

Duplicate screening

Duplicate data extraction

Adequate description of included studies

Report sources of funding

Risk of bias assessment for meta-analysis

Analysis of heterogeneity

Report conflicts of interest