| 年度 | 实际值 |
|---|---|
| 1992 | 8.4 |
| 1993 | 8.2 |
| 1994 | |
| 1995 | 8.07 |
| 1996 | 9.01 |
| 1997 | 6.12 |
| 1998 | 4.01 |
| 1999 | 5.57 |
| 2000 | 17.82 |
| 2001 | 6.67 |
| 2002 | 10.7 |
| 2003 | 5.57 |
| 2004 | 5.14 |
| 2005 | 11.52 |
| 2006 | 4.5 |
| 2007 | 5.79 |
| 2008 | 6.25 |
| 2009 | |
| 2010 | 4.39 |
| 2011 | 5.9 |
| 2012 | 7.1 |
| 2013 | 7.5 |
| 2014 | 22.3 |
| 2015 | 11.25 |
| 2016 | 10.28 |
| 2017 | 4.38 |
| 2018 | 11.38 |