| 年度 | 实际值 |
|---|---|
| 1992 | 7.7 |
| 1993 | 7 |
| 1994 | |
| 1995 | 7.46 |
| 1996 | 7.91 |
| 1997 | 9.88 |
| 1998 | 4.39 |
| 1999 | 12.6 |
| 2000 | 18.34 |
| 2001 | 8.88 |
| 2002 | 8.69 |
| 2003 | 8.13 |
| 2004 | 6.83 |
| 2005 | 4.41 |
| 2006 | 7.37 |
| 2007 | 5.76 |
| 2008 | 24.17 |
| 2009 | |
| 2010 | 28.58 |
| 2011 | 16.3 |
| 2012 | 14.7 |
| 2013 | 21 |
| 2014 | 8.8 |
| 2015 | 15.99 |
| 2016 | 11.75 |
| 2017 | 12.13 |
| 2018 | 14.47 |