| 年度 | 实际值 |
|---|---|
| 1995 | 33.5 |
| 1996 | 30.6 |
| 1997 | 27.9 |
| 1998 | 29.8 |
| 1999 | 28.7 |
| 2000 | 27.9 |
| 2001 | 24.45 |
| 2002 | 25.35 |
| 2003 | 20.9 |
| 2004 | 25.43 |
| 2005 | 27.47 |
| 2006 | 26.33 |
| 2007 | 24.02 |
| 2008 | 23.71 |
| 2009 | |
| 2010 | 21.34 |
| 2011 | 20.38 |
| 2012 | 19.86 |
| 2013 | 19.17 |
| 2014 | 17.63 |
| 2015 | 16.97 |
| 2016 | 15.85 |
| 2017 | |
| 2018 | 12.25 |