| 年度 | 实际值 |
|---|---|
| 1992 | 8 |
| 1993 | 5.2 |
| 1994 | |
| 1995 | 2.64 |
| 1996 | 3.1 |
| 1997 | 4.07 |
| 1998 | 5.1 |
| 1999 | 4.82 |
| 2000 | 3.87 |
| 2001 | 4.03 |
| 2002 | 3.9 |
| 2003 | 4.74 |
| 2004 | 4.9 |
| 2005 | 6.36 |
| 2006 | 12.78 |
| 2007 | 10.68 |
| 2008 | 9.6 |
| 2009 | |
| 2010 | 8.56 |
| 2011 | 12.1 |
| 2012 | 8.8 |
| 2013 | 16 |
| 2014 | 13.5 |
| 2015 | 12.65 |
| 2016 | 11.19 |
| 2017 | 2.22 |
| 2018 | 8.33 |