| 年度 | 实际值 |
|---|---|
| 1992 | 4.3 |
| 1993 | 2.5 |
| 1994 | |
| 1995 | 3.86 |
| 1996 | 4.23 |
| 1997 | |
| 1998 | |
| 1999 | |
| 2000 | 5.59 |
| 2001 | 5.28 |
| 2002 | 6.77 |
| 2003 | 5.87 |
| 2004 | 7.25 |
| 2005 | 8.11 |
| 2006 | 8.1 |
| 2007 | 12.24 |
| 2008 | 9.51 |
| 2009 | |
| 2010 | 10.44 |
| 2011 | 3.7 |
| 2012 | 9.8 |
| 2013 | 13.6 |
| 2014 | 12.1 |
| 2015 | 11.68 |
| 2016 | 10.65 |
| 2017 | 0.28 |
| 2018 | 3.52 |