| 年度 | 实际值 |
|---|---|
| 1992 | 10.7 |
| 1993 | 8.2 |
| 1994 | |
| 1995 | 5.69 |
| 1996 | 4.98 |
| 1997 | 5.52 |
| 1998 | 2.66 |
| 1999 | 7.16 |
| 2000 | 7.52 |
| 2001 | 7.16 |
| 2002 | 7.72 |
| 2003 | 6.35 |
| 2004 | 6.55 |
| 2005 | 6.76 |
| 2006 | 8.57 |
| 2007 | 7.9 |
| 2008 | 7.44 |
| 2009 | |
| 2010 | 7.05 |
| 2011 | 9.1 |
| 2012 | 2.9 |
| 2013 | 12.3 |
| 2014 | 10.3 |
| 2015 | 11.53 |
| 2016 | 12.22 |
| 2017 | 5.26 |
| 2018 | 8.3 |