| 年度 | 实际值 |
|---|---|
| 1992 | 11.1 |
| 1993 | 9.4 |
| 1994 | |
| 1995 | 8.91 |
| 1996 | 8.36 |
| 1997 | |
| 1998 | |
| 1999 | 10.51 |
| 2000 | 11.06 |
| 2001 | 9.13 |
| 2002 | 7.94585050029429 |
| 2003 | 7.99 |
| 2004 | 10.63 |
| 2005 | 10.89 |
| 2006 | 8.8 |
| 2007 | 7.04546079779917 |
| 2008 | 6.97 |
| 2009 | 7.87 |
| 2010 | 6.83097856049876 |
| 2011 | 6.43 |
| 2012 | 7.37 |
| 2013 | 6.61 |
| 2014 | 6.15 |
| 2015 | 5.43 |