| 1998 | 2005 | 2012 | ||||
| Markets | Mean | Std. Dev. | Mean | Std. Dev. | Mean | Std. Dev. |
| All markets | 128.845 | 20.167 | −15.347 | 17.394 | −138.309 | 17.670 |
| By distance-haul categories | ||||||
| Short-haul distance | 93.165 | 38.692 | −20.048 | 6.274 | −139.226 | 20.502 |
| Mid-haul distance | 129.821 | 22.633 | −12.826 | 20.503 | −138.258 | 18.601 |
| Long-haul distance | 130.613 | 10.477 | −17.958 | 13.019 | −138.284 | 15.746 |
| No. of markets | ||||||
| Short-haul distance | 10 | 12 | 17 | |||
| Mid-haul markets | 139 | 214 | 238 | |||
| Long-haul markets | 125 | 185 | 143 | |||
| Total | 274 | 411 | 398 | |||