| 年度 | 实际值 |
|---|---|
| 1992 | 17 |
| 1993 | |
| 1994 | |
| 1995 | 17.5 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 18.1 |
| 2000 | 18.2786 |
| 2001 | 18.3344 |
| 2002 | 18.4055 |
| 2003 | 18.5266 |
| 2004 | 18.786 |
| 2005 | 19.58 |
| 2006 | 19.51 |
| 2007 | 19.6 |
| 2008 | 19.621472842496 |
| 2009 | 20.6526 |
| 2010 | 20.6473 |
| 2011 | 20.8486 |
| 2012 | 20.8446 |
| 2013 | 21.0719 |
| 2014 | 18.69 |
| 2015 | 18.7496273844229 |
| 2016 | 21 |
| 2017 | 21 |