| 年度 | 实际值 |
|---|---|
| 1992 | 24.3 |
| 1993 | |
| 1994 | |
| 1995 | 25.2 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 26.1 |
| 2000 | 26.762 |
| 2001 | 26.7605 |
| 2002 | 26.8007 |
| 2003 | 26.8081 |
| 2004 | 27.0437 |
| 2005 | 27.04 |
| 2006 | 26.98 |
| 2007 | 27.11 |
| 2008 | 27.14149737505 |
| 2009 | 28.1578 |
| 2010 | 28.4748 |
| 2011 | 29.1414 |
| 2012 | 29.4421 |
| 2013 | 29.6102 |
| 2014 | 26.54 |
| 2015 | 26.5843111326855 |
| 2016 | 30 |
| 2017 | 30 |