Is there a state-dependent optimal interval for firms’ R&D investment? Evidence from China

This study sheds light on the existence of a time-varying and state-dependent optimal interval of research and development (R&D) investment in which firms can maximize the positive effect of R&D on their performance. We develop a panel kink threshold regression model with multiple covariate-dependent thresholds to capture a time-varying optimal interval of R&D investment. Based on the data of A-share listed firms in Shanghai and Shenzhen in China from 2012 to 2020, we provide empirical evidence supporting a state-dependent optimal interval of R&D investment, above or below which R&D is significantly negatively associated with performance. Specifically, the lower bound of the optimal interval (R&D barrier point) is counter-cyclical, while the upper bound of the interval (R&D saturation point) is pro-cyclical. Our study provides a new approach to understand the time-varying and state-dependent threshold effect in the R&D investment, hence contributing to the research and practice of determining the optimal R&D investment.