| 年度 | 实际值 |
|---|---|
| 1992 | 17.1 |
| 1993 | |
| 1994 | |
| 1995 | 17.7 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 18.3 |
| 2000 | 18.6018 |
| 2001 | 18.8434 |
| 2002 | 19.1549 |
| 2003 | 19.2866 |
| 2004 | 19.736 |
| 2005 | 19.9 |
| 2006 | 19.84 |
| 2007 | 19.93 |
| 2008 | 19.9129478144 |
| 2009 | 20.4483 |
| 2010 | 20.3845 |
| 2011 | 20.4997 |
| 2012 | 20.0235 |
| 2013 | 20.3951 |
| 2014 | 19.57 |
| 2015 | 19.6088098056096 |
| 2016 | 20 |
| 2017 | 20 |