| 年度 | 实际值 |
|---|---|
| 1992 | 14.2 |
| 1993 | |
| 1994 | |
| 1995 | 14 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 14.1 |
| 2000 | 14.44 |
| 2001 | 14.5 |
| 2002 | 14.46 |
| 2003 | 14.45 |
| 2004 | 14.39 |
| 2005 | 14.45 |
| 2006 | 14.42 |
| 2007 | 14.46 |
| 2008 | 14.48 |
| 2009 | 14.62 |
| 2010 | 14.51 |
| 2011 | 14.74 |
| 2012 | 14.69 |
| 2013 | 14.23 |
| 2014 | 14.18 |
| 2015 | 14.16 |
| 2016 | 14 |
| 2017 | 14 |