| 年度 | 实际值 |
|---|---|
| 1992 | 4.6 |
| 1993 | 4.8 |
| 1994 | |
| 1995 | 4.43 |
| 1996 | 4.71 |
| 1997 | 3.92 |
| 1998 | 6.25 |
| 1999 | 3.62 |
| 2000 | 3.57 |
| 2001 | 2.9 |
| 2002 | 2.7 |
| 2003 | 2.31 |
| 2004 | 4 |
| 2005 | 3.3 |
| 2006 | 2.84 |
| 2007 | 3.34 |
| 2008 | 2.76 |
| 2009 | |
| 2010 | 3.4 |
| 2011 | 4.6 |
| 2012 | 3.9 |
| 2013 | 4.7 |
| 2014 | 6.9 |
| 2015 | 4.23 |
| 2016 | 7.51 |
| 2017 | 6.12 |
| 2018 | 6.23 |