| Year | |
|---|---|
| 1989 | 1,593.1 |
| 1990 | 1,593.1 |
| 1991 | 1,292.0 |
| 1992 | 990.8 |
| 1993 | 689.7 |
| 1994 | 689.7 |
| 1995 | 689.7 |
| 1996 | 558.3 |
| 1997 | 585.3 |
| 1998 | 585.3 |
| 1999 | 547.4 |
| 2000 | 535.8 |
| 2001 | 535.8 |
| 2002 | 495.5 |
| 2003 | 495.5 |
| 2004 | 790.7 |
| 2005 | 676.0 |
| 2006 | 676.0 |
| 2007 | 676.0 |
| 2008 | 676.0 |
| 2009 | 697.3 |
| 2010 | 689.2 |
| 2011 | 689.2 |
| 2012 | 689.2 |
| 2013 | 689.2 |
| 2014 | 689.2 |
| 2015 | 616.8 |
| 2016 | 616.8 |
| 2017 | 616.8 |