| 年度 | 实际值 |
|---|---|
| 1992 | 23.1 |
| 1993 | |
| 1994 | |
| 1995 | 22.9 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 22.8 |
| 2000 | 22.8453 |
| 2001 | 22.8343 |
| 2002 | 22.8434 |
| 2003 | 22.8803 |
| 2004 | 22.964 |
| 2005 | 19.07 |
| 2006 | 19.0927 |
| 2007 | 19.11 |
| 2008 | 19.146 |
| 2009 | 23.5351 |
| 2010 | 23.6106 |
| 2011 | 23.6237 |
| 2012 | 23.632 |
| 2013 | 23.867 |
| 2014 | 19.39 |
| 2015 | 19.4467 |
| 2016 | 23 |
| 2017 | 23 |