| 年度 | 实际值 |
|---|---|
| 1992 | 38.9 |
| 1993 | |
| 1994 | |
| 1995 | 38.7 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 39.0001 |
| 2000 | 39.4043 |
| 2001 | 39.3639 |
| 2002 | 39.376 |
| 2003 | 39.4307 |
| 2004 | 39.4446 |
| 2005 | 39.1831 |
| 2006 | 39.3003 |
| 2007 | 39.5599 |
| 2008 | 39.7924 |
| 2009 | 39.9289 |
| 2010 | 39.528 |
| 2011 | 39.6861 |
| 2012 | 39.9204 |
| 2013 | 39.7489 |
| 2014 | 39.1989 |
| 2015 | 39.0276 |
| 2016 | 39 |
| 2017 | 39 |