| 年度 | 实际值 |
|---|---|
| 1992 | 11 |
| 1993 | |
| 1994 | |
| 1995 | 11.3 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 10.9666 |
| 2000 | 10.3286 |
| 2001 | 11.4236 |
| 2002 | 10.294 |
| 2003 | 9.7385 |
| 2004 | 9.7119 |
| 2005 | 9.7259 |
| 2006 | 10.2855 |
| 2007 | 9.7182 |
| 2008 | 9.7507 |
| 2009 | 9.2994 |
| 2010 | 8.9938 |
| 2011 | 8.9211 |
| 2012 | 8.7661 |
| 2013 | 8.6502 |
| 2014 | 8.3847 |
| 2015 | 8.3972 |