| 年度 | 实际值 |
|---|---|
| 1992 | 22.7 |
| 1993 | |
| 1994 | |
| 1995 | 23 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 24.0997 |
| 2000 | 24.2851 |
| 2001 | 24.3399 |
| 2002 | 24.4566 |
| 2003 | 24.5708 |
| 2004 | 24.6848 |
| 2005 | 24.7167 |
| 2006 | 25.4354 |
| 2007 | 25.7458 |
| 2008 | 26.222 |
| 2009 | 26.4419 |
| 2010 | 26.1568 |
| 2011 | 25.767 |
| 2012 | 25.8761 |
| 2013 | 26.0276 |
| 2014 | 26.1159 |
| 2015 | 25.39 |
| 2016 | 26 |
| 2017 | 25 |