| 年度 | 实际值 |
|---|---|
| 1992 | 14.2 |
| 1993 | |
| 1994 | |
| 1995 | 14.4 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 15 |
| 2000 | 15.3 |
| 2001 | 15.3384 |
| 2002 | 15.4521 |
| 2003 | 15.5632 |
| 2004 | 15.4643 |
| 2005 | 15.6523 |
| 2006 | 15.8313 |
| 2007 | 16.0008 |
| 2008 | 16.1304 |
| 2009 | 16.3177 |
| 2010 | 16 |
| 2011 | 17 |
| 2012 | 16 |
| 2013 | 16 |
| 2014 | 17 |
| 2015 | 17 |
| 2016 | 17 |
| 2017 | 18 |