| 年度 | 实际值 |
|---|---|
| 1992 | 63.8 |
| 1993 | |
| 1994 | |
| 1995 | 63.2 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 60.8 |
| 2000 | 60.5 |
| 2001 | 60 |
| 2002 | 59.4 |
| 2003 | 58.7 |
| 2004 | 58.1 |
| 2005 | 57.7 |
| 2006 | 57.4 |
| 2007 | 57.33 |
| 2008 | 57.4 |
| 2009 | 57.3 |
| 2010 | 57.3 |
| 2011 | 57.1 |
| 2012 | 56.7 |
| 2013 | 56.4 |
| 2014 | 56.2 |
| 2015 | 55.83 |
| 2016 | 55.5834 |
| 2017 | 55.1 |
| 2018 | 54.7486 |