The Nuclear Arms Control Index (NACI): A dataset on the design of the nuclear regime complex

Scholarship on legalization and nuclear proliferation often relies on aggregate measures of institutional design that obscure variation across provisions. We introduce the Nuclear Arms Control Index (NACI), a dataset of 91 nuclear arms control and nonproliferation instruments (1945–2025), and an original nuclear weapons capability life-cycle framework that categorizes the different stages of nuclear control. NACI codes 53 variables capturing life-cycle stages and additional institutional design features across instruments and time. Clause-level indicators are generated through a large language model-assisted, application programming interface-based analysis of the full treaty corpus and then adjudicated and verified by the authors. We illustrate three empirical applications by showing associations between life-cycle indicators and entry into force, replicating Kreps to disaggregate legalization measures into treaty-specific components associated with arms control cooperation, and replicating Katagiri to replace the Treaty on the Non-Proliferation of Nuclear Weapons membership with design-level provisions. These applications show how NACI enables provision-level research on the design of nuclear arms control.