| 年度 | 实际值 |
|---|---|
| 1992 | 14.6 |
| 1993 | 14.7 |
| 1994 | |
| 1995 | 13.71 |
| 1996 | 13.67 |
| 1997 | 12.33 |
| 1998 | 5.88 |
| 1999 | 7.34 |
| 2000 | 22.37 |
| 2001 | 6.57 |
| 2002 | 6.82 |
| 2003 | 10.45 |
| 2004 | 6.19 |
| 2005 | 5.48 |
| 2006 | 5.18 |
| 2007 | 5.19 |
| 2008 | 5.63 |
| 2009 | |
| 2010 | 4.66 |
| 2011 | 4.6 |
| 2012 | 5.8 |
| 2013 | 6.1 |
| 2014 | 7.3 |
| 2015 | 7.22 |
| 2016 | 7.14 |
| 2017 | 8.29 |
| 2018 | 11.59 |