| Dependent Variable: TFP | (1) | (2) | (3) | (4) |
| DID | −0.0844*** | −0.0598*** |
|
|
|
| (0.0133) | (0.0146) |
|
|
| DDD |
|
| −0.0905*** | −0.0753*** |
|
|
|
| (0.0116) | (0.0122) |
| Control variables | No | Yes | No | Yes |
| County fixed effect | Yes | Yes | Yes | Yes |
| Year fixed effect | Yes | Yes | Yes | Yes |
| Observations | 1920 | 1920 | 1920 | 1920 |
| R-squared | 0.2004 | 0.1378 | 0.1589 | 0.1321 |