| 年度 | 实际值 |
|---|---|
| 1992 | 12.1 |
| 1993 | 8.4 |
| 1994 | |
| 1995 | 8.5 |
| 1996 | 9.12 |
| 1997 | 8.9 |
| 1998 | 4.44 |
| 1999 | 8.12 |
| 2000 | 31.02 |
| 2001 | 7.68 |
| 2002 | 8.2 |
| 2003 | 7.98 |
| 2004 | 8.02 |
| 2005 | 7.81 |
| 2006 | 8.35 |
| 2007 | 10.71 |
| 2008 | 10.17 |
| 2009 | |
| 2010 | 11.55 |
| 2011 | 11 |
| 2012 | 13.9 |
| 2013 | 5.5 |
| 2014 | 5.8 |
| 2015 | 5.38 |
| 2016 | 6.85 |
| 2017 | 6.72 |
| 2018 | 6.35 |