| 年度 | 实际值 |
|---|---|
| 1992 | 10.1 |
| 1993 | 9.8 |
| 1994 | |
| 1995 | 9.89 |
| 1996 | 10.97 |
| 1997 | 11 |
| 1998 | 5.55 |
| 1999 | 9.34 |
| 2000 | 12.04 |
| 2001 | 7.12 |
| 2002 | 6.33 |
| 2003 | 6.61 |
| 2004 | 5.34 |
| 2005 | 5.54 |
| 2006 | 6.55 |
| 2007 | 6.56 |
| 2008 | 6.59 |
| 2009 | |
| 2010 | 6.56 |
| 2011 | 11.7 |
| 2012 | 6 |
| 2013 | 5.3 |
| 2014 | 8.7 |
| 2015 | 8.09 |
| 2016 | 7.74 |
| 2017 | 1.55 |
| 2018 | 6.93 |