| 年度 | 实际值 |
|---|---|
| 1992 | 2.8 |
| 1993 | |
| 1994 | |
| 1995 | 2.8 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 2.8576 |
| 2000 | 2.7903 |
| 2001 | 2.7641 |
| 2002 | 2.7889 |
| 2003 | 2.8365 |
| 2004 | 2.8848 |
| 2005 | 2.9204 |
| 2006 | 2.9716 |
| 2007 | 3.0312 |
| 2008 | 3.0716 |
| 2009 | 3.0783 |
| 2010 | 3.0737 |
| 2011 | 3.1109 |
| 2012 | 3.1197 |
| 2013 | 3.1378 |
| 2014 | 3.1353 |
| 2015 | 3.1349 |
| 2016 | 3 |
| 2017 | 3 |