| 年度 | 实际值 |
|---|---|
| 1995 | 16.5 |
| 1996 | 15.2 |
| 1997 | 17.22 |
| 1998 | 15.5 |
| 1999 | 15.9 |
| 2000 | 15.9 |
| 2001 | 14.61 |
| 2002 | 14.06 |
| 2003 | 13.21 |
| 2004 | 13.31 |
| 2005 | 16.13 |
| 2006 | 14.93 |
| 2007 | 15.34 |
| 2008 | 15.39 |
| 2009 | |
| 2010 | 13.02 |
| 2011 | 12.42 |
| 2012 | 12.35 |
| 2013 | 12.44 |
| 2014 | 11.82 |
| 2015 | 11.6 |
| 2016 | 12.18 |
| 2017 | |
| 2018 | 9.37 |