| 年度 | 实际值 |
|---|---|
| 1995 | 31.8 |
| 1996 | 30.6 |
| 1997 | 29.37 |
| 1998 | 32.3 |
| 1999 | 32.6 |
| 2000 | 32.5 |
| 2001 | 32 |
| 2002 | 30.76 |
| 2003 | 26.67 |
| 2004 | 24.96 |
| 2005 | 35.37 |
| 2006 | 35.06 |
| 2007 | 33.25 |
| 2008 | 32.68 |
| 2009 | |
| 2010 | 27.33 |
| 2011 | 26.27 |
| 2012 | 25.69 |
| 2013 | 33.15 |
| 2014 | 35.81 |
| 2015 | 42.15 |
| 2016 | 42.57 |
| 2017 | |
| 2018 | 37.05 |