| 年度 | 实际值 |
|---|---|
| 1992 | 14.2 |
| 1993 | |
| 1994 | |
| 1995 | 14.4 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 14.6 |
| 2000 | 14.7 |
| 2001 | 15 |
| 2002 | 14.7 |
| 2003 | 15 |
| 2004 | 15 |
| 2005 | 15.1 |
| 2006 | 15.2 |
| 2007 | 15.3353 |
| 2008 | 15.42 |
| 2009 | 15.5 |
| 2010 | 15.3893 |
| 2011 | 15.53 |
| 2012 | 15.4147 |
| 2013 | 15.59 |
| 2014 | 15.63 |
| 2015 | 15.65 |
| 2016 | 15.7224 |
| 2017 | 16 |