| Year | control | control | control | control |
| Costant | −1.470 | −1.129 | 1.601** | 0.551 |
|
| (−1.423) | (−1.544) | (2.382) | (0.803) |
| Pseudo/R2 | 0.0042 | 0.0042 | 0.0032 | 0.0022 |
| N | 607 | 607 | 607 | 607 |