Effects of knowledge spillovers between competitors on patent quality: what patent citations reveal about a global duopoly

This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness [Grant Number ECO2016-79436-R], [AEI/FEDER/UE]. Previous versions of the paper were presented at the 2018 Technology Transfer Society Annual Conference (Valencia), the 2019 International Open and User Innovation Conference (Utretcht), and the 2019 annual International Conference on Economics and Security (Madrid). The authors express their thanks to colleagues at these conferences for their helpful suggestions. The authors are also very grateful to two anonymous reviewers for their constructive and insightful comments.