| 年度 | 实际值 |
|---|---|
| 1992 | 7.8 |
| 1993 | |
| 1994 | |
| 1995 | 7.9 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 7.8999 |
| 2000 | 7.65 |
| 2001 | 7.8458 |
| 2002 | 7.8728 |
| 2003 | 7.7907 |
| 2004 | 7.8226 |
| 2005 | 7.8745 |
| 2006 | 7.9833 |
| 2007 | 8.0908 |
| 2008 | 8.145 |
| 2009 | 8.1799 |
| 2010 | 8.238 |
| 2011 | 8.2902 |
| 2012 | 8.2489 |
| 2013 | 8.3192 |
| 2014 | 8.3762 |
| 2015 | 8.3229 |
| 2016 | 8 |
| 2017 | 8 |