| 年度 | 实际值 |
|---|---|
| 1992 | 16 |
| 1993 | |
| 1994 | |
| 1995 | 16.3 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 17 |
| 2000 | 17.1118 |
| 2001 | 17.1524 |
| 2002 | 17.2227 |
| 2003 | 17.25 |
| 2004 | 17.2824 |
| 2005 | 17.04 |
| 2006 | 16.95 |
| 2007 | 17.03 |
| 2008 | 17.05578782629 |
| 2009 | 18.3347 |
| 2010 | 18.2395 |
| 2011 | 18.4524 |
| 2012 | 18.5535 |
| 2013 | 18.7473 |
| 2014 | 17.01 |
| 2015 | 17.0556408082438 |
| 2016 | 19 |
| 2017 | 19 |