A map of what we know — and what we don't
An evidence gap map (EGM) is a grid. Down the side: the things you could do — interventions. Across the top: the things you might change — outcomes. In each cell, a bubble shows how much rigorous evidence exists for that pairing, and how confident we can be in it. Big confident bubbles mean "well studied, works." Empty cells — the gaps — mean "nobody really knows yet." The empty cells are often the most important thing on the map.
Click any bubble in the map above to see what the evidence says about that intervention–outcome pairing, how confident we can be, and where to read more.
Four moves of a careful reader
Find the big green bubbles
Well-studied pairings with consistent effects. This is where "what works" is on solid ground — act here with confidence.
Distrust a single study
A small bubble is one or two trials. One striking result is a hypothesis, not a finding. Confidence comes from replication.
Hunt for the empty cells
The gaps are where confident claims outrun the evidence. "Everyone knows X works" over an empty cell is a research agenda, not a fact.
Mind the context
Evidence travels imperfectly. What worked in one country, scale, or population may not transfer. The map narrows uncertainty; it never removes it.
Authoritative, continuously-updated maps
This page teaches the idea. For live evidence on a real decision, go to the source — these institutions build and maintain rigorous evidence gap maps and systematic reviews.