| 年度 | 实际值 |
|---|---|
| 1992 | 12.3 |
| 1993 | 10.4 |
| 1994 | |
| 1995 | 8.78 |
| 1996 | 7.57 |
| 1997 | 7.34 |
| 1998 | 5.09 |
| 1999 | 7.67 |
| 2000 | 6.96 |
| 2001 | 7.12 |
| 2002 | 7.45 |
| 2003 | 7.39 |
| 2004 | 7.27 |
| 2005 | 6.36 |
| 2006 | 7.68 |
| 2007 | 7.41 |
| 2008 | 7.42 |
| 2009 | |
| 2010 | 7.83 |
| 2011 | 9.5 |
| 2012 | 4.1 |
| 2013 | 9 |
| 2014 | 12.4 |
| 2015 | 13.47 |
| 2016 | 17.55 |
| 2017 | 4.97 |
| 2018 | 4.96 |