| 年度 | 实际值 |
|---|---|
| 1992 | 8.5 |
| 1993 | 6.5 |
| 1994 | |
| 1995 | 5.48 |
| 1996 | 6.05 |
| 1997 | 5.34 |
| 1998 | 4.11 |
| 1999 | 4.19 |
| 2000 | 7.89 |
| 2001 | 4.76 |
| 2002 | 5.47 |
| 2003 | 5.61 |
| 2004 | 5.29 |
| 2005 | 4.83 |
| 2006 | 5.3 |
| 2007 | 5.95 |
| 2008 | 5.45 |
| 2009 | |
| 2010 | 5.11 |
| 2011 | 7.5 |
| 2012 | 8.6 |
| 2013 | 9.1 |
| 2014 | 10.6 |
| 2015 | 11.59 |
| 2016 | 14.44 |
| 2017 | 18 |
| 2018 | 15.43 |