| 年度 | 实际值 |
|---|---|
| 1992 | 13.2 |
| 1993 | |
| 1994 | |
| 1995 | 13.5 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 14.507 |
| 2000 | 13.1212 |
| 2001 | 13.601 |
| 2002 | 13.6025 |
| 2003 | 13.5433 |
| 2004 | 14.2961 |
| 2005 | 14.7236 |
| 2006 | 14.6657 |
| 2007 | 16.0394 |
| 2008 | 16.4097 |
| 2009 | 15.9444 |
| 2010 | 15.6297 |
| 2011 | 15.8537 |
| 2012 | 15.8331 |
| 2013 | 18.3048 |
| 2014 | 18.5621 |
| 2015 | 18.6053 |