Bilateral treaty networks: assessing cooperative spillover in defense and investment

The potential for mutual influence or “spillover” between economic and security cooperation is a long-standing area of interest for policymakers and scholars alike. This paper examines how network dynamics affect spillover. We focus on two prominent types of formal bilateral cooperation—defense cooperation agreements (DCAs) and bilateral investment treaties (BITs)—both of which have proliferated dramatically in the post-Cold War international system. We argue that existing theoretical and empirical approaches to economic-security spillover focus too strictly on influences at the bilateral level. As with other forms of international cooperation, BITs and DCAs comprise larger international networks. Governments develop portfolios of BITs or DCAs with distinct structural goals in mind, and they implement specific strategies in pursuing those goals. With BITs, governments follow a network-hierarchy strategy that allows them to influence treaty design and protect their firms. In DCAs, governments instead favor a network-community strategy focused on pooling collective security goods among groups of like-minded collaborators. When these network strategies complement one another, they promote cooperative economic-security spillover. When they conflict, however, they inhibit spillover, such that cooperation in economic or security issues discourages cooperation in the opposing issue area.