| 1996 | 1997 | 1998 | 1999 | 2000 | |
| JAN | 9.1 | 8.7 | 10.0 | 9.2 | |
| FEB | 10.8 | 8.9 | 10.1 | 8.4 | |
| MAR | 15.3 | 9.2 | 11.0 | 15.2 | |
| APR | 13.6 | 15.9 | 11.9 | 17.6 | |
| MAY | 23.1 | 19.3 | 19.2 | 16.2 | 21.3 |
| JUN | 23.4 | 22.5 | 25.6 | 21.2 | 21.3 |
| JUL | 22.9 | 24.9 | 24.1 | 21.8 | 20.9 |
| AUG | 23.5 | 22.8 | 20.7 | 18.9 | 21.4 |
| SEP | 17.9 | 21.8 | 18.7 | 18.2 | 19.3 |
| OCT | 17.7 | 16.3 | 17.1 | 15.3 | 16.3 |
| NOV | 13.9 | 13.0 | 17.5 | 12.7 | 7.2 |
| DEC | 11.0 | 8.9 | 12.4 | 7.6 | 6.6 |