| 年度 | 实际值 |
|---|---|
| 1992 | 22.9 |
| 1993 | |
| 1994 | |
| 1995 | 23.3 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 23 |
| 2000 | 22.8536 |
| 2001 | 22.7502 |
| 2002 | 22.7403 |
| 2003 | 22.696 |
| 2004 | 23.1213 |
| 2005 | 21.93 |
| 2006 | 21.91 |
| 2007 | 21.97 |
| 2008 | 22.04 |
| 2009 | 23.8964 |
| 2010 | 23.9461 |
| 2011 | 24.2003 |
| 2012 | 24.3699 |
| 2013 | 24.6236 |
| 2014 | 22.28 |
| 2015 | 22.34 |
| 2016 | 25 |
| 2017 | 25 |