Note(s): This table reports the regression results of the robustness test (including redefining the dependent variable test in column (1), redefining the independent variable test in column (2) and (3), the fixed effect model test in column (4), shortening the research interval test in column (5) and introducing the missing variables test in column (6)). See Table 1 for detailed descriptions of all variables. All specifications include year and industry fixed effects. Standard errors after robust adjustment are clustered at the firm-year level. The t-value is in parentheses. ***, ** and * indicate statistical significance at the 0.01, 0.05 and 0.10 levels, respectively (two-tailed tests)