| 年度 | 实际值 |
|---|---|
| 1993 | 23.4 |
| 1994 | |
| 1995 | 26.2 |
| 1996 | 27.2 |
| 1997 | 28.2 |
| 1998 | 29.2 |
| 1999 | 30.2 |
| 2000 | 30.1 |
| 2001 | 2.1 |
| 2002 | |
| 2003 | 33.51 |
| 2004 | 34.6 |
| 2005 | 31 |
| 2006 | 35.03 |
| 2007 | 37.09 |
| 2008 | 43.17 |
| 2009 | |
| 2010 | 37.54 |
| 2011 | 44.7 |
| 2012 | 43.16 |
| 2013 | 45.28 |
| 2014 | 45.36 |
| 2015 | 45.6 |
| 2016 | 45.79 |
| 2017 | 43.41 |
| 2018 | 43.68 |