| 1 | 1998 | 502.0 | | | | | | | | |
| 2 | 1999 | 556.1 | | | | | | | | |
| 3 | 2000 | 529.1 | | | | | | | | |
| 4 | 2001 | 491.0 | | | | | | | | |
| 5 | 2002 | 462.2 | | | | | | | | |
| 6 | 2003 | 545.1 | | | | | | | | |
| 7 | 2004 | 549.1 | | | | | | | | |
| 8 | 2005 | 516.1 | | | | | | | | |
| 9 | 2006 | 513.1 | | | | | | | | |
| 10 | 2007 | 497.0 | 26.0% | 61.9% | 45.2% | 75.0% | 83.8% | 81.5% | 53.5% | 23.6 |
| 11 | 2008 | 484.1 | 26.3% | 61.7% | 44.8% | 62.1% | 85.5% | 78.9% | 52.1% | 24.3 |
| 12 | 2009 | 457.1 | 26.3% | 61.0% | 44.6% | 65.7% | 87.3% | 81.3% | 52.8% | 23.2 |
| 13 | 2010 | 454.0 | 29.1% | 63.4% | 46.7% | 59.9% | 85.2% | 77.6% | 51.5% | 23.8 |
| 14 | 2011 | 391.0 | 26.3% | 62.5% | 45.3% | 63.9% | 85.6% | 79.6% | 52.6% | 24.3 |