| 年度 | 实际值 |
|---|---|
| 1992 | 13.5 |
| 1993 | 10.3 |
| 1994 | |
| 1995 | 10.27 |
| 1996 | 10.46 |
| 1997 | 10.7 |
| 1998 | 2.21 |
| 1999 | 10.2 |
| 2000 | 20.52 |
| 2001 | 8.33 |
| 2002 | 6.26 |
| 2003 | 8.26 |
| 2004 | 6.84 |
| 2005 | 7.06 |
| 2006 | 8.85 |
| 2007 | 8.03 |
| 2008 | 7.4 |
| 2009 | |
| 2010 | 8.39 |
| 2011 | 8.1 |
| 2012 | 9.9 |
| 2013 | 8.4 |
| 2014 | 12.1 |
| 2015 | 6.78 |
| 2016 | 9.22 |
| 2017 | 3.29 |
| 2018 | 7.01 |