Collaboration between public sector organizations is typically understood as a response to complexity. Agencies collaborate in order to address complex, cross-cutting policy needs that cannot be met individually. However, when organizational size is a constraining factor in public service efficiency, collaboration can also reduce costs by capturing scale economies unavailable to organizations of sub-optimal size. Using organization theory, the article conceptualizes these two different triggers for public sector collaboration, and builds a framework for tracing their wider impact upon the formation, operation, and outcome of inter-agency partnerships. The framework is illustrated, and its implications for future research are explored
