Reframing the Diversification–Performance Nexus in Insurance: A Systematic Review of Governance, Risk Management, and Institutional Contingency

Diversification is one of the most contested strategic choices in insurance: it can stabilize risk and income, but it can also intensify complexity, agency problems, and governance failure. After five decades of research, the insurance diversification–performance literature remains divided between diversification premium, diversification discount, and non-linear interpretations. This systematic review of 56 empirical studies reframes the debate by asking not whether diversification creates value, but when, why, and under what governance and risk-management conditions it does so. Guided by PRISMA 2020, the review develops a multi-level institutional-contingency framework that integrates institutional theory, the resource-based view, and agency theory. The framework explains how institutional environments shape the strategic logic of diversification, how enterprise risk management, technological infrastructure, and human capital determine execution capacity, and how weak governance and managerial misalignment can turn diversification into value destruction. Covering product, geographic, human capital, and technological diversification, the review shows that premiums, discounts, and non-linear effects coexist because diversification outcomes depend on institutional context, governance quality, ERM maturity, and firm capabilities rather than diversification per se. The study contributes to research on corporate governance and risk management at financial institutions by positioning diversification as a strategic, governance-sensitive risk-management decision in insurance firms.