| 年度 | 实际值 |
|---|---|
| 1993 | 30.5 |
| 1994 | |
| 1995 | 29 |
| 1996 | 31 |
| 1997 | 31 |
| 1998 | 25.2 |
| 1999 | 31.5 |
| 2000 | 32 |
| 2001 | 2.26 |
| 2002 | |
| 2003 | 35.59 |
| 2004 | 40.4 |
| 2005 | 30 |
| 2006 | 32.59 |
| 2007 | 39.32 |
| 2008 | 35.26 |
| 2009 | |
| 2010 | 38.44 |
| 2011 | 40.89 |
| 2012 | 39.92 |
| 2013 | 45.31 |
| 2014 | 45.09 |
| 2015 | 45.23 |
| 2016 | 41.78 |
| 2017 | 43.07 |
| 2018 | 43.37 |