| 年度 | 实际值 |
|---|---|
| 1993 | 31.6 |
| 1994 | |
| 1995 | 26.4 |
| 1996 | 27.5 |
| 1997 | 27.5 |
| 1998 | 23.6 |
| 1999 | 25.2 |
| 2000 | 24.4 |
| 2001 | 1.68666666666667 |
| 2002 | |
| 2003 | 26.51 |
| 2004 | 26.05 |
| 2005 | 27 |
| 2006 | 25.05 |
| 2007 | 34 |
| 2008 | 36.03 |
| 2009 | |
| 2010 | 37.49 |
| 2011 | 38.32 |
| 2012 | 39.19 |
| 2013 | 39.73 |
| 2014 | 40.11 |
| 2015 | 40.9 |
| 2016 | 40.97 |
| 2017 | 40.75 |
| 2018 | 40.75 |