title: Geopolitical risk contagion across strategic sectors: Nonlinear evidence from defense, cybersecurity, energy, and raw materials
abstract: This study investigates the effect of geopolitical risk on the market volatility of four strategic sectors - defense, cybersecurity, energy, and critical raw materials - using a sample of 90 companies and ETFs over the 2014-2025 period. Applying Quantile-on-Quantile Connectedness (QQC) and Causality-in-Quantiles (CiQ) methods, the study captures the asymmetric and nonlinear relationships between geopolitical uncertainty and market volatility. The findings show that defense and cybersecurity sect
journal: PLoS ONE