| 年度 | 实际值 |
|---|---|
| 1995 | 35.8 |
| 1996 | 33.6 |
| 1997 | 31.69 |
| 1998 | 31.8 |
| 1999 | 28.2 |
| 2000 | 27.2 |
| 2001 | 25.82 |
| 2002 | 24.91 |
| 2003 | 24.05 |
| 2004 | 24.67 |
| 2005 | 25.35 |
| 2006 | 22.89 |
| 2007 | 22.47 |
| 2008 | 20.81 |
| 2009 | |
| 2010 | 15.22 |
| 2011 | 14.52 |
| 2012 | 13.94 |
| 2013 | 13.64 |
| 2014 | 12.69 |
| 2015 | 12.4 |
| 2016 | 12.02 |
| 2017 | |
| 2018 | 11.24 |