| 年度 | 实际值 |
|---|---|
| 1992 | 11 |
| 1993 | 11.9 |
| 1994 | |
| 1995 | 11.85 |
| 1996 | 7.84 |
| 1997 | |
| 1998 | |
| 1999 | |
| 2000 | 8.34 |
| 2001 | 6.76 |
| 2002 | 6.28 |
| 2003 | 5.59 |
| 2004 | 5.61 |
| 2005 | 5.81 |
| 2006 | 6.29 |
| 2007 | 6.43 |
| 2008 | 6.69 |
| 2009 | 6.69 |
| 2010 | 5.26 |
| 2011 | 5.28 |
| 2012 | 5.29 |
| 2013 | 5.31 |
| 2014 | 5.33 |
| 2015 | 5.5 |
| 2016 | 8.35 |
| 2017 | -0.79 |
| 2018 | 4.66 |