| 年度 | 实际值 |
|---|---|
| 1992 | 6 |
| 1993 | 7 |
| 1994 | |
| 1995 | 6.05 |
| 1996 | 5.52 |
| 1997 | 6.76 |
| 1998 | 3.98 |
| 1999 | 6.93 |
| 2000 | 20.16 |
| 2001 | 8.09 |
| 2002 | 8.86 |
| 2003 | 9.79 |
| 2004 | 11.1 |
| 2005 | 3.41 |
| 2006 | 13.31 |
| 2007 | 15.02 |
| 2008 | 13.37 |
| 2009 | |
| 2010 | 18.73 |
| 2011 | 11.9 |
| 2012 | 6.6 |
| 2013 | 6.6 |
| 2014 | 6.7 |
| 2015 | 8.43 |
| 2016 | 7.08 |
| 2017 | 7.99 |
| 2018 | 9.75 |