| 年度 | 实际值 |
|---|---|
| 1992 | 5.8 |
| 1993 | |
| 1994 | |
| 1995 | 5.8 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 6.3672 |
| 2000 | 6.5681 |
| 2001 | 6.7224 |
| 2002 | 6.828 |
| 2003 | 6.9494 |
| 2004 | 7.0459 |
| 2005 | 7.0731 |
| 2006 | 7.2054 |
| 2007 | 7.4034 |
| 2008 | 7.4712 |
| 2009 | 7.5714 |
| 2010 | 7.6948 |
| 2011 | 7.8511 |
| 2012 | 7.8986 |
| 2013 | 8.038 |
| 2014 | 8.1014 |
| 2015 | 8.1147 |
| 2016 | 8 |
| 2017 | 8 |