| 年度 | 实际值 |
|---|---|
| 1992 | 13.2 |
| 1993 | 10.9 |
| 1994 | |
| 1995 | 9.78 |
| 1996 | 12.43 |
| 1997 | 9.41 |
| 1998 | 3.65 |
| 1999 | 5.47 |
| 2000 | 14.62 |
| 2001 | 6.04 |
| 2002 | 6.85 |
| 2003 | 6.82 |
| 2004 | 3.96 |
| 2005 | 6.41 |
| 2006 | 6.32 |
| 2007 | 6.75 |
| 2008 | 7.12 |
| 2009 | |
| 2010 | 7.5 |
| 2011 | 7.4 |
| 2012 | 10.6 |
| 2013 | 18.4 |
| 2014 | 12.4 |
| 2015 | 8.35 |
| 2016 | 11.86 |
| 2017 | 5.63 |
| 2018 | 10.97 |