In this work, we measure the reactivity of Italian !rms value added to the dynamics of Germany, US and China’s GDP during the 2005-2017 period. In particular, on the basis of “granular” approach recently developed in the empirical literature, we derive a !rm-level measure of shock sensitivity, allowing to obtain the overall Italian business system’s reactivity by merely adding up individual !rm responses. Our results show that Italian internationalized !rms were more sensitive to a GDP increase in the United States, rather than in Germany and China. In general, the contribution to overall reactivity derives predominantly from !rms belonging to trade internationalization classes (Only importers, Only exporters, Two-way traders), while the contribution of !rms with productive internationalization forms (Multinational linkages) appears to be very limited. "ere emerges a relevant contribution from Two-way traders, due to a higher concentration in this class of highly reactive !rms, especially in industrial sectors deeply involved in GVCs. "is result is more evident when we consider !rms always present throughout the 2005-2017 period: two recessions a$ected more severely classes with the less advanced forms of internationalization, where the presence of highly reactive !rms is lower.