| 年度 | 实际值 |
|---|---|
| 1992 | 27.6 |
| 1993 | |
| 1994 | |
| 1995 | 28.5 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 29.2 |
| 2000 | 29.3929 |
| 2001 | 29.5998 |
| 2002 | 29.6698 |
| 2003 | 29.7953 |
| 2004 | 30.0599 |
| 2005 | 29.63 |
| 2006 | 29.73 |
| 2007 | 29.87 |
| 2008 | 29.97 |
| 2009 | 31.7514 |
| 2010 | 32.0863 |
| 2011 | 32.3814 |
| 2012 | 32.662 |
| 2013 | 33.0618 |
| 2014 | 33.03 |
| 2015 | 33.18 |
| 2016 | 34 |
| 2017 | 34 |