“…The choice of control variables is based on three main considerations: First, at the level of firm characteristics, environmental investment is an investment behavior of firms and is necessarily influenced by firm fundamentals, so with reference to previous literature (Porter and Linde, 1995;Tang et al, 2013;Hu et al, 2017;Feng and Sun, 2020), we control for variables such as firm age (Age), firm size (Size), firm growth (Growth), profitability (ROA), financial leverage (Lev), capital expenditure (Capx) and operating cash flow (Cfo). Second, at the level of internal corporate governance, factors such as shareholding structure, board structure, and executive characteristics can indirectly affect the environmental governance level by influencing firms' investment decisions (Carl et al, 2012;Tao and Liu, 2013;Schaltenbrand et al, 2018;Dyck et al, 2019;Zhao and Mao, 2022), so we also control for the proportion of institutional shareholding (INSR), board size (Board), the proportion of independent directors (Indp), and dual employment (Dual) variables. Third, at the level of the firm's external environment, according to previous literature (Orsato, 2006;Gao and Zheng, 2017;Zhou and Shen, 2019), the degree of market competition of the enterprise and the strength of government environmental regulation also have an impact on the environmental governance of a firm at a certain period, so we also control for the variables of industry concentration (HHI) and the environmental regulation effects (ER).…”