| 年度 | 实际值 |
|---|---|
| 1992 | 20 |
| 1993 | |
| 1994 | |
| 1995 | 20 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 14.6029 |
| 2000 | 14.59 |
| 2001 | 23.4902 |
| 2002 | 23.6854 |
| 2003 | 23.4203 |
| 2004 | 23.7416 |
| 2005 | 23.9926 |
| 2006 | 24.7277 |
| 2007 | 24.5107 |
| 2008 | 24.5553 |
| 2009 | 24.6187 |
| 2010 | 25.161 |
| 2011 | 23.6266 |
| 2012 | 23.7168 |
| 2013 | 23.2616 |
| 2014 | 18.6496 |
| 2015 | 20.7295 |