This study reassesses the influential public goods theory of alliances, specifically addressing its central claim about free-riding by small participants. Previous tests suffered from model specification and generalizability issues, leaving little reliable evidence for this idea despite its prevalence.

➡️ Data & Methods

* Examines 204 alliances formed between 1919 and 2007

* Uses state-level GDP contribution to measure economic weight

* Compares military spending changes across allied states based on their economic share

➡️ Key Findings

🔍 Contrary to the theory's prediction, little evidence supports free-riding by states with a small GDP share.

➡️ Why It Matters

🤔 These results suggest that alliance security is not purely captured as a public good and may involve complex bargaining dynamics among members. The findings question the robustness of economic calculations in explaining strategic behavior within alliances.