| 年度 | 实际值 |
|---|---|
| 1993 | 27.9 |
| 1994 | |
| 1995 | 24.3 |
| 1996 | 24.3 |
| 1997 | 30.3 |
| 1998 | 30.4 |
| 1999 | 30.4 |
| 2000 | 30.4 |
| 2001 | 1.85333333333333 |
| 2002 | |
| 2003 | 22.79 |
| 2004 | 32.83 |
| 2005 | 35 |
| 2006 | 35.59 |
| 2007 | 37.69 |
| 2008 | 39.57 |
| 2009 | |
| 2010 | 38.98 |
| 2011 | 24.99 |
| 2012 | 30.79 |
| 2013 | 32.47 |
| 2014 | 32.47 |
| 2015 | 28.86 |
| 2016 | 30.14 |
| 2017 | 37.65 |
| 2018 | 41.25 |