| 年度 | 实际值 |
|---|---|
| 1992 | 12.6 |
| 1993 | 11.6 |
| 1994 | |
| 1995 | 8.02 |
| 1996 | 6.29 |
| 1997 | 5.15 |
| 1998 | 4.68 |
| 1999 | 7.4 |
| 2000 | 12.98 |
| 2001 | 9.6 |
| 2002 | 7.44 |
| 2003 | 7.73 |
| 2004 | 6.79 |
| 2005 | 8.27 |
| 2006 | 12.52 |
| 2007 | 13.31 |
| 2008 | 12.39 |
| 2009 | |
| 2010 | 31.73 |
| 2011 | 9.4 |
| 2012 | |
| 2013 | 15.9 |
| 2014 | 23.6 |
| 2015 | 14.89 |
| 2016 | 13.02 |
| 2017 | 4.23 |
| 2018 | 13.69 |