Background: The role of the state, the effectiveness of its institutions and its legitimacy in the eyes of its citizens are central to determining a country’s prospects for stability and development. Addressing the challenges that developing countries face, promoting prosperity and ensuring that prosperity is equitably shared, requires effective governance.

Objectives: This evidence-gap map (EGM) is intended to consolidate evidence on the effect of interventions to improve state-society relations in low- and middle-income countries. It relies on systematic methods to find effectiveness evidence and make it easily accessible. In so doing, it identifies evidence clusters and evidence gaps, and indicates where future research could focus.

Methods: This EGM identifies, categorises and displays systematic reviews and impact evaluations in a matrix that categorises evidence into intervention and outcome types. It is based on a systematic search of published and unpublished literature and the application of systematic inclusion criteria and data extraction processes.

Results: We identified 18 systematic reviews, two systematic review protocols and 365 impact evaluations – 305 completed and 60 ongoing. The number of studies being published has increased year-on-year since 2000. However, the distribution of studies across countries, regions and intervention types is uneven. For example, over half were conducted in only eight countries. Most systematic reviews examine interventions pertaining to public institutions and services; very few look at political processes, despite the relatively large number of impact evaluations in this area.

Conclusions: Although an increasing number of systematic reviews and impact evaluations addressing this topic are being published, some clear gaps in the evidence remain. There is limited or no evidence on many countries with large populations that face substantial governance challenges. Even where that evidence base is strongest, important policy questions remain. There are also important gaps in the systematic review evidence base.