| 年度 | 实际值 |
|---|---|
| 1992 | 10.4 |
| 1993 | 10.3 |
| 1994 | |
| 1995 | 9.25 |
| 1996 | 9.78 |
| 1997 | 9.85 |
| 1998 | 5.22 |
| 1999 | 7.04 |
| 2000 | 12.74 |
| 2001 | 5.25 |
| 2002 | 4.04 |
| 2003 | 4.98 |
| 2004 | 4.55 |
| 2005 | 4.41 |
| 2006 | 7.24 |
| 2007 | 5.06 |
| 2008 | 8.22 |
| 2009 | |
| 2010 | 12.82 |
| 2011 | 8.4 |
| 2012 | 5.7 |
| 2013 | 10.7 |
| 2014 | 8.7 |
| 2015 | 8.8 |
| 2016 | 31.09 |
| 2017 | 12.76 |
| 2018 | 12.28 |