| 年度 | 实际值 |
|---|---|
| 1992 | 11.9 |
| 1993 | 12 |
| 1994 | |
| 1995 | 11.46 |
| 1996 | 11.76 |
| 1997 | 11.28 |
| 1998 | 4.94 |
| 1999 | 6.83 |
| 2000 | 7.2 |
| 2001 | 4.97 |
| 2002 | 4.74 |
| 2003 | 5.4 |
| 2004 | 5.19 |
| 2005 | 5.28 |
| 2006 | 8.53 |
| 2007 | 6.11 |
| 2008 | 6.01 |
| 2009 | |
| 2010 | 6.94 |
| 2011 | 6.8 |
| 2012 | 7.6 |
| 2013 | 7.6 |
| 2014 | 8.8 |
| 2015 | 9.36 |
| 2016 | 14.7 |
| 2017 | 8.23 |
| 2018 | 13.91 |