| 年度 | 实际值 |
|---|---|
| 1992 | 16.1 |
| 1993 | |
| 1994 | |
| 1995 | 16 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 11.8681 |
| 2000 | 12.0215 |
| 2001 | 16.9196 |
| 2002 | 16.821 |
| 2003 | 16.7926 |
| 2004 | 16.9949 |
| 2005 | 17.0155 |
| 2006 | 16.8318 |
| 2007 | 16.8991 |
| 2008 | 17.4021 |
| 2009 | 17.7561 |
| 2010 | 18.145 |
| 2011 | 18.5868 |
| 2012 | 18.8373 |
| 2013 | 18.9068 |
| 2014 | 17.9861 |
| 2015 | 17.9831 |