Critical Realist Analysis of Health Policy Implementation Failure in Nigeria: The Case of the National Health Insurance Scheme

Despite two decades of operation, the National Health Insurance Scheme has achieved fewer than 5 percent population coverage in Nigeria, constituting one of the most significant health policy implementation failures in sub-Saharan Africa. This study applies a Critical Realist framework to explain the mechanisms, contexts, and structures underlying the National Health Insurance Scheme's implementation failure across Nigeria's six geopolitical zones. The research design combines a retrospective policy document analysis spanning 2005 to 2024, 80 semi-structured interviews with current and former policymakers, scheme managers, healthcare providers, and enrolled and non-enrolled community members, and six months of ethnographic fieldwork at scheme management offices in Lagos, Abuja, and Kaduna. Retroductive reasoning is employed to identify causal mechanisms operating at the structural (legislative, regulatory, and political economy), contextual (state governance, market structure, and social trust), and agential (individual provider and enrollee behaviour) levels. The Realistic Evaluation methodology of Pawson and Tilley provides the analytical scaffold for developing context-mechanism-outcome configurations. The study's original contribution lies in applying Critical Realism to a major African health policy case, generating a replicable analytical framework for health policy implementation research in low- and middle-income countries. Findings will provide evidence for a comprehensive National Health Insurance Scheme reform agenda, informing the recently passed National Health Insurance Authority Act. Keywords: National Health Insurance Scheme, policy implementation failure, Critical Realism, health financing, Nigeria.