| 年度 | 实际值 |
|---|---|
| 1992 | 18.1 |
| 1993 | 20.1 |
| 1994 | |
| 1995 | 8.47 |
| 1996 | 6.65 |
| 1997 | 2.93 |
| 1998 | 5.58 |
| 1999 | 8.28 |
| 2000 | 8.27 |
| 2001 | 10.57 |
| 2002 | 8.37 |
| 2003 | 9.89 |
| 2004 | 8.64 |
| 2005 | 9.58 |
| 2006 | 11.65 |
| 2007 | 13.21 |
| 2008 | 10.63 |
| 2009 | |
| 2010 | 14.09 |
| 2011 | 10 |
| 2012 | 1.6 |
| 2013 | 15.7 |
| 2014 | 37.2 |
| 2015 | 13.59 |
| 2016 | 12.98 |
| 2017 | 5.38 |
| 2018 | 13.94 |