| 年度 | 实际值 |
|---|---|
| 1993 | 4.8 |
| 1994 | |
| 1995 | 7.6 |
| 1996 | 6.5 |
| 1997 | 7.5 |
| 1998 | 7.6 |
| 1999 | 11.9 |
| 2000 | 13 |
| 2001 | .886666666666667 |
| 2002 | |
| 2003 | 13.06 |
| 2004 | 14 |
| 2005 | 15 |
| 2006 | 18.37 |
| 2007 | 18.58 |
| 2008 | 20.21 |
| 2009 | |
| 2010 | 15.7 |
| 2011 | 33.21 |
| 2012 | 32.94 |
| 2013 | 32.71 |
| 2014 | 33.57 |
| 2015 | 31.13 |
| 2016 | 33.71 |
| 2017 | 36.25 |
| 2018 | 36.21 |