| 年度 | 实际值 |
|---|---|
| 1992 | 25.9 |
| 1993 | |
| 1994 | |
| 1995 | 26.6 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 26.7 |
| 2000 | 26.9 |
| 2001 | 27 |
| 2002 | 26.7 |
| 2003 | 27 |
| 2004 | 27 |
| 2005 | 26.9 |
| 2006 | 27.2 |
| 2007 | 27.6406 |
| 2008 | 27.83 |
| 2009 | 27.5 |
| 2010 | 27.0943 |
| 2011 | 27.37 |
| 2012 | 26.5256 |
| 2013 | 26.66 |
| 2014 | 27.04 |
| 2015 | 27.16 |
| 2016 | 27.2884 |
| 2017 | 27 |