| 年度 | 实际值 |
|---|---|
| 1993 | 7.7 |
| 1994 | |
| 1995 | 20.1 |
| 1996 | 38.7 |
| 1997 | 21 |
| 1998 | 20.6 |
| 1999 | 20.8 |
| 2000 | 21.3 |
| 2001 | 1.14666666666667 |
| 2002 | |
| 2003 | 17.87 |
| 2004 | 32.51 |
| 2005 | 49 |
| 2006 | 27 |
| 2007 | 24.19 |
| 2008 | 29.33 |
| 2009 | |
| 2010 | 26.67 |
| 2011 | 24.83 |
| 2012 | 23.42 |
| 2013 | 22.7 |
| 2014 | 24.26 |
| 2015 | 23.61 |
| 2016 | 22.18 |
| 2017 | 33.68 |
| 2018 | 41.32 |