| 年度 | 实际值 |
|---|---|
| 1992 | 14.4 |
| 1993 | 14.6 |
| 1994 | |
| 1995 | 14.81 |
| 1996 | 15.12 |
| 1997 | 11.03 |
| 1998 | 3.31 |
| 1999 | 10.97 |
| 2000 | 9.7 |
| 2001 | 7.46 |
| 2002 | 7.13 |
| 2003 | 6.54 |
| 2004 | 6.26 |
| 2005 | 6.29 |
| 2006 | 6.67 |
| 2007 | 6.71 |
| 2008 | 6.82 |
| 2009 | 6.91 |
| 2010 | 5.55 |
| 2011 | 5.57 |
| 2012 | 5.62 |
| 2013 | 5.64 |
| 2014 | 5.65 |
| 2015 | 5.73 |
| 2016 | 10.13 |
| 2017 | 2.24 |
| 2018 | 9.44 |