| 1 | Very light | 50% |
| 2 | Light | 10% |
| 3 | Moderate | 20% |
| 4 | Average | 40% |
| 5 | Quite severe | 60% |
| 6 | Severe | 100% |
| 7 | Chronic | 150% |
| 8 | Exceptional | 300% |