| 年度 | 实际值 |
|---|---|
| 1995 | 37.7 |
| 1996 | 31.2 |
| 1997 | 22.16 |
| 1998 | 25.5 |
| 1999 | 24.5 |
| 2000 | 21.3 |
| 2001 | 18.84 |
| 2002 | 17.96 |
| 2003 | 16.77 |
| 2004 | 15.79 |
| 2005 | 14.52 |
| 2006 | 13.63 |
| 2007 | 14.03 |
| 2008 | 12.6 |
| 2009 | |
| 2010 | 11.69 |
| 2011 | 13.07 |
| 2012 | 13.09 |
| 2013 | 12.98 |
| 2014 | 11.15 |
| 2015 | 1121 |
| 2016 | 10.86 |
| 2017 | 10.17 |
| 2018 | 9.48 |