| 年度 | 实际值 |
|---|---|
| 1995 | 32.6 |
| 1996 | 27.2 |
| 1997 | 38.53 |
| 1998 | 23.8 |
| 1999 | 22.8 |
| 2000 | 22.7 |
| 2001 | 26.9 |
| 2002 | 24.82 |
| 2003 | 27.23 |
| 2004 | 30.28 |
| 2005 | 34.1 |
| 2006 | 34.02 |
| 2007 | 33.73 |
| 2008 | 34.94 |
| 2009 | |
| 2010 | 38.34 |
| 2011 | 33.48 |
| 2012 | 33.07 |
| 2013 | 32.91 |
| 2014 | 36.16 |
| 2015 | 39.43 |
| 2016 | 40.73 |
| 2017 | 41.31 |
| 2018 | 40.15 |