| 年度 | 实际值 |
|---|---|
| 1992 | 13.6 |
| 1993 | 13.3 |
| 1994 | |
| 1995 | 12.16 |
| 1996 | 12.65 |
| 1997 | 11.46 |
| 1998 | 4.43 |
| 1999 | 12 |
| 2000 | 12.26 |
| 2001 | 8.59 |
| 2002 | 7.31 |
| 2003 | 9.7 |
| 2004 | 9.15 |
| 2005 | 7.46 |
| 2006 | 7.71 |
| 2007 | 6.33 |
| 2008 | 8.88 |
| 2009 | |
| 2010 | 13.43 |
| 2011 | 14.9 |
| 2012 | 10.4 |
| 2013 | 7.5 |
| 2014 | 5.7 |
| 2015 | 6.36 |
| 2016 | 8.34 |
| 2017 | 9.59 |
| 2018 | 16.29 |