| 年度 | 实际值 |
|---|---|
| 1992 | 63.5 |
| 1993 | 17.73 |
| 1994 | 18.28 |
| 1995 | 18.94 |
| 1996 | 20.4 |
| 1997 | 22.97 |
| 1998 | 24.75 |
| 1999 | 26.2 |
| 2000 | 29.3 |
| 2001 | 30.3736 |
| 2002 | 30.8204 |
| 2003 | 30.0533 |
| 2004 | 28.6867 |
| 2005 | 29.0515 |
| 2006 | 29.9306 |
| 2007 | 29.0634 |
| 2008 | 29.7434 |
| 2009 | 29.8324 |
| 2010 | 29.83 |
| 2011 | 30.9 |
| 2012 | 29 |
| 2013 | 30.3 |
| 2014 | 30.7 |
| 2015 | 31.4 |
| 2016 | 32 |
| 2017 | 32 |
| 2018 | 33 |