| 年度 | 实际值 |
|---|---|
| 1992 | 13 |
| 1993 | 12.6 |
| 1994 | |
| 1995 | 12.86 |
| 1996 | 12.88 |
| 1997 | 12.4 |
| 1998 | 5.57 |
| 1999 | 18.23 |
| 2000 | 17.86 |
| 2001 | 2.75 |
| 2002 | 3.57 |
| 2003 | 4.6 |
| 2004 | 3.72 |
| 2005 | 4.59 |
| 2006 | 5.75 |
| 2007 | 3.14 |
| 2008 | 3.69 |
| 2009 | |
| 2010 | 13.38 |
| 2011 | 7.8 |
| 2012 | 7.9 |
| 2013 | 10.5 |
| 2014 | 7.4 |
| 2015 | 17.63 |
| 2016 | 9.02 |
| 2017 | 9.82 |
| 2018 | 6.76 |