| (1) | (2) | (3) |
| OLS | FE | GMM |
| 0.498** | 0.279** | 0.409** |
| 0.282** | 0.098** | 0.366** |
企业固定效应? | no | yes | yes |
时间效应 | yes | yes | yes |
| 0.382 | 0.459 | 0.399 |
观察值 | 43773 | 43773 | 32382 |