| 年度 | 实际值 |
|---|---|
| 1992 | 9 |
| 1993 | 10.8 |
| 1994 | |
| 1995 | 10.71 |
| 1996 | 10.42 |
| 1997 | 9.91 |
| 1998 | 5.31 |
| 1999 | 8.33 |
| 2000 | 10.42 |
| 2001 | 7.72 |
| 2002 | 7.25 |
| 2003 | 7.56 |
| 2004 | 5.8 |
| 2005 | 7.73 |
| 2006 | 12.68 |
| 2007 | 12.72 |
| 2008 | 15.14 |
| 2009 | |
| 2010 | 14.28 |
| 2011 | 15.3 |
| 2012 | 16.4 |
| 2013 | 16.2 |
| 2014 | 15.8 |
| 2015 | 18.86 |
| 2016 | 15.96 |
| 2017 | 10.48 |
| 2018 | 4.38 |