Firm-level reaction functions with contemporaneous R&D decisions of the mean rival firm.

Characterizing dyads by their median Region, for both σgr and σlev to measure product rivalry. IV GMM regressions with Pre-Sample Mean and , respectively.以二元组（dyads）的中位区域对其进行表征，借助σgr与σlev分别衡量产品竞争强度。采用工具变量广义矩估计（IV-GMM）回归方法，并分别结合样本前均值（Pre-Sample Mean）开展相关分析。