| 年度 | 实际值 |
|---|---|
| 1992 | 3 |
| 1993 | |
| 1994 | |
| 1995 | 2.7 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 2.5263 |
| 2000 | 2.5618 |
| 2001 | 2.5771 |
| 2002 | 2.6434 |
| 2003 | 2.9305 |
| 2004 | 3.0281 |
| 2005 | 3.8211 |
| 2006 | 3.7001 |
| 2007 | 3.8911 |
| 2008 | 2.8901 |
| 2009 | 3.6375 |
| 2010 | 3.8176 |
| 2011 | 3.7584 |
| 2012 | 3.7379 |
| 2013 | 3.853 |
| 2014 | 3.3067 |
| 2015 | 3.8417 |