| 年度 | 实际值 |
|---|---|
| 1993 | 25.5 |
| 1994 | |
| 1995 | 24.8 |
| 1996 | 29.9 |
| 1997 | 27.2 |
| 1998 | 27.5 |
| 1999 | 26.9 |
| 2000 | 27.1 |
| 2001 | 1.84666666666667 |
| 2002 | |
| 2003 | 31 |
| 2004 | 32.35 |
| 2005 | 38 |
| 2006 | 37.48 |
| 2007 | 37.11 |
| 2008 | 37.23 |
| 2009 | |
| 2010 | 38.73 |
| 2011 | 40.52 |
| 2012 | 40.3 |
| 2013 | 42.19 |
| 2014 | 39.66 |
| 2015 | 39.7 |
| 2016 | 39.7 |
| 2017 | 39.91 |
| 2018 | 41.95 |