The tone of turbulence: Japan’s diplomatic posture toward China under political uncertainty and Kantei centralization

This study investigates how domestic political uncertainty and economic policy uncertainty (EPU) shape Japan’s diplomatic posture toward China across 456 monthly observations (1987–2024). Challenging structural realist accounts that privilege external economic forces, it introduces the Adjusted News-based Economic and Regime Opinion Polls (ANEROP) index as a measure of political uncertainty and employs a Vector Autoregression (VAR) model with GDELT-derived diplomatic tone as the outcome measure. The results show that ANEROP has significant Granger-causal effects on shifts in diplomatic tone, whereas EPU has only a marginal effect, highlighting the primacy of domestic political uncertainty in Japan’s China policy. Regression discontinuity and subperiod VAR analyses identify a structural break at the 2001 Kantei centralization reform, after which political uncertainty becomes an active driver of diplomatic recalibration. These findings contribute to a domestic-institutional approach to foreign policy analysis by showing how institutional centralization conditions the foreign policy effects of domestic political uncertainty.