| 年度 | 实际值 |
|---|---|
| 1993 | 11.8 |
| 1994 | |
| 1995 | 9.21 |
| 1996 | 6.15 |
| 1997 | 9.46 |
| 1998 | 5.07 |
| 1999 | 5.17 |
| 2000 | 3.35 |
| 2001 | 3.52 |
| 2002 | 3.99 |
| 2003 | 7.71 |
| 2004 | 2.7 |
| 2005 | 5.18 |
| 2006 | 4.06 |
| 2007 | 3.8 |
| 2008 | 1.77 |
| 2009 | |
| 2010 | 5.61 |
| 2011 | 7.7 |
| 2012 | 5.5 |
| 2013 | 4.6 |
| 2014 | 7.5 |
| 2015 | 15.93 |
| 2016 | 8.73 |
| 2017 | 7.43 |
| 2018 | 5.24 |