| Year effect | Yes | Yes | Yes | Yes | Yes | Yes |
| Code effect | Yes | Yes | Yes | Yes | Yes | Yes |
| N | 7384 | 5784 | 7384 | 5784 | 7384 | 5784 |
| R-sq | 0.5358 | 0.5751 | 0.5566 | 0.6008 | 0.5574 | 0.6025 |