Just as my father taught me when I start a jigsaw I first sort the pieces: corners, edges, and others. If possible sort the others as you go into obvious groups, like the blue bits for the sky.

The Centre for Homelessness Impact’s evidence maps are part of putting together the evidence jigsaw for homelessness. Here are all the pieces of evidence. How do we fit them together?

There is a caveat here, as we cannot truly say “here are all the pieces”. Doing a jigsaw with missing pieces is at best annoying and often difficult. The Centre’s maps have many of the pieces. But we can’t say all.

Having so many pieces in one place is itself a very valuable resource. The effectiveness map has 227 studies and the implementation issues map around 270 – ‘around’ as are still discussing some studies which fall in a grey area between research and evaluation. So between them, the two maps have close to 500 studies of interventions to improve the welfare of those experiencing or at risk of homelessness in one place. That is a lot of pieces! The maps – and the underlying database which will be launched later this year – are part of the Centre’s mission to make evidence more accessible to policymakers and practitioners.

We know there are missing pieces and appeal to users to let us know what they are. Thanks to those who have been doing so.

But the puzzle is to fit the pieces together. As I started by saying, the first step is to sort the pieces. That is what the evidence maps do. In fact, we have two puzzles. The ‘what works’ puzzle: the effectiveness map. And the ‘why do things work or not’ puzzle: the implementation issues map. So the two maps first sort the pieces into those two separate piles corresponding to the two separate puzzles.

For each puzzle, the evidence and gap maps are our way of sorting the pieces. We have done that. So the contribution of the Centre to date has been to collect in one piece a large quantity of relevant evidence – relevant as we have screened it to only include evaluations of interventions, not more general research.  And we have sorted (structured) that evidence into two maps making it easier to navigate.

We admit it hasn’t always been that easy to figure out which are the most appropriate labels of the piles, often as a single piece often seems to belong in more than one pile. Again, any feedback on the way we have done it is welcome.

Having sorted them the next step is to put the pieces together so the picture of what the evidence says emerges. Again, like a puzzle, we put the pieces together in a systematic way by working on a particular bit of the puzzle, putting together the evidence sorted into a particular pile. We are putting the evidence together by commissioning systematic reviews. Here the jigsaw analogy breaks down, as our mixed method reviews will use pieces from both maps. The first reviews we are doing are on the effectiveness of Housing First, and of discharge programmes, and the third review on cost analysis.

The findings from the review will feed into our Intervention Tool which presents the full picture of the evidence of what works and why for homelessness. Please watch this space to see the picture as it emerges.