| 年度 | 实际值 |
|---|---|
| 1993 | 26.1 |
| 1994 | |
| 1995 | 25.1 |
| 1996 | 26.2 |
| 1997 | 27.7 |
| 1998 | 30.6 |
| 1999 | 33.9 |
| 2000 | 44.8 |
| 2001 | 2.61333333333333 |
| 2002 | |
| 2003 | 31.16 |
| 2004 | 32.46 |
| 2005 | 31 |
| 2006 | 34.55 |
| 2007 | 34.81 |
| 2008 | 38.23 |
| 2009 | |
| 2010 | 38.2 |
| 2011 | 40.09 |
| 2012 | 40.32 |
| 2013 | 39.98 |
| 2014 | 39.92 |
| 2015 | 39.91 |
| 2016 | 40.33 |
| 2017 | 40.75 |
| 2018 | 41.27 |