| 年度 | 实际值 |
|---|---|
| 1993 | 20.2 |
| 1994 | |
| 1995 | 22.6 |
| 1996 | 25.7 |
| 1997 | 24.6 |
| 1998 | 25 |
| 1999 | 25.1 |
| 2000 | 25.1 |
| 2001 | 1.67333333333333 |
| 2002 | |
| 2003 | 27.41 |
| 2004 | 28.78 |
| 2005 | 32 |
| 2006 | 32.26 |
| 2007 | 40.56 |
| 2008 | 38.03 |
| 2009 | |
| 2010 | 42.13 |
| 2011 | 44.03 |
| 2012 | 42.59 |
| 2013 | 40.24 |
| 2014 | 40.24 |
| 2015 | 39.31 |
| 2016 | 39.05 |