Table 1.
Definition and calculation method of main variables.
| Variable type | Variable name | Variable definition | Variable symbol |
|---|---|---|---|
| Explained variable | Innovation investment | R&D expenditures / Operating income (%) | Input |
| Explanatory variable | The interaction term of the group dummy variable and the time dummy variable | DID | |
| Moderating variable | Absorptive capacity | The ratio of R&D personnel (%) | AC |
| Control variables | Firm size | Ln (total assets) | Size |
| Asset-liability ratio | Total debt / Total assets (%) | Lev | |
| Cash flow ratio | Cash from operating activities / Total assets (%) | Cash | |
| Return on equity | Net profit / Stockholders’ equity balance (%) | Roe | |
| Firm’s growth ability | Operating income growth rate (%) | Growth | |
| Ownership concentration | The shareholding ratio of the top 10 major shareholder (%) | Shareh10 | |
| Firm’s age | Ln (Sample period-establishment period+1) | Age |