| Year | |
|---|---|
| 1989 | 309.8 |
| 1990 | 309.8 |
| 1991 | 366.0 |
| 1992 | 422.2 |
| 1993 | 478.4 |
| 1994 | 522.9 |
| 1995 | 574.2 |
| 1996 | 658.1 |
| 1997 | 658.1 |
| 1998 | 691.1 |
| 1999 | 691.1 |
| 2000 | 718.5 |
| 2001 | 718.5 |
| 2002 | 854.0 |
| 2003 | 854.0 |
| 2004 | 854.0 |
| 2005 | 906.1 |
| 2006 | 921.2 |
| 2007 | 921.2 |
| 2008 | 921.2 |
| 2009 | 928.1 |
| 2010 | 969.1 |
| 2011 | 1,038.7 |
| 2012 | 1,036.5 |
| 2013 | 1,032.4 |
| 2014 | 923.6 |
| 2015 | 1,084.4 |
| 2016 | 1,104.4 |
| 2017 | 1,104.4 |