| 年度 | 实际值 |
|---|---|
| 1992 | 13.2 |
| 1993 | 10.1 |
| 1994 | |
| 1995 | 9.01 |
| 1996 | 7.56 |
| 1997 | 7.65 |
| 1998 | 4.95 |
| 1999 | 8.07 |
| 2000 | 7.33 |
| 2001 | 7.67 |
| 2002 | 7.9 |
| 2003 | 7.53 |
| 2004 | 7.32 |
| 2005 | 6.12 |
| 2006 | 8.07 |
| 2007 | 8.87 |
| 2008 | 7.68 |
| 2009 | |
| 2010 | 8.64 |
| 2011 | 8.2 |
| 2012 | 3.3 |
| 2013 | 9.5 |
| 2014 | 10.4 |
| 2015 | 11.54 |
| 2016 | 12 |
| 2017 | 4.92 |
| 2018 | 5.12 |