Studying collaborative governance has become a booming business. However, the empirical literature still struggles to produce robust generalizations and cumulative knowledge that link contextual, situational and institutional design factors to processes and outcomes. We still have not mustered the broad and deep evidence base that will really help us sort fact from fiction and identify more and less productive approaches to collaboration. The current empirical evidence in the study of

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... ive governance consists chiefly of small-N case studies or large-N surveys. The challenge is to move from case-based, mid-range theory building to more largeN-driven systematic theory-testing, while also retaining the rich contextual and process insights that only small-N studies tend to yield. This article, and the articles in the accompanying special issue, introduces an attempt to provide this middle groundthe Collaborative Governance Case Database. The database has been developed to serve as a free common pool resource for researchers to systematically collect and compare high-quality collaborative governance case studies. This article is an introduction to the database, exploring its design, opportunities and limitations. This article is also an invitation; inviting all researchers to freely use the cases in the database for their own research interest and to help strengthening the database by adding new cases there are eager to share with colleagues. KEYWORDS Collaborative governance; case studies; case database; open data; new methodologies Finding the middle ground between richness and generalization Studying 'collaborative governance' has become a booming business, much like the study of closely related phenomena like 'policy networks' and 'partnerships' was in the 1990s and 2000s.