| Variable symbol | variable name | definition |
| NP | innovation output | logarithm of number of patent applications plus 1 |
| RD | innovation input | ratio of R & D investment to operating revenue |
| group | whether to implement private placement | virtual variable, if the enterprise implements private placement, the value is 1; otherwise, the value is 0 |
| time | observation period | virtual variable, if the enterprise implements private placement in the current year, the value of this year and subsequent years is 1; otherwise, the value is 0 |
| topsh | the largest shareholder’s shareholding ratio | ratio of the number of shares held by the largest shareholder to the total number of shares of the company |
| size | company size | logarithm of total assets |
| gp | income growth rate | ratio of increase in operating revenue of the year to total operating revenue of the previous year |
| roa | return on assets | ratio of net profit to total assets |
| lev | asset liability ratio | ratio of total liabilities to total assets |
| bm | book to market ratio | ratio of book value to market value |
| age | age of company | logarithm of observation year minus listing year plus 1 |
| board | sector characteristics | virtual variable, if the enterprise is listed on GEM or SME board, it is 1, otherwise it is 0 |
| nature | nature of ownership | virtual variable, 1 for state-owned enterprises and 0 for non-state-owned enterprises |
| yd | year | virtual variable |
| id | industry | virtual variable |