| 年度 | 实际值 |
|---|---|
| 1995 | 42 |
| 1996 | 39.6 |
| 1997 | 37.52 |
| 1998 | 34.6 |
| 1999 | 32.7 |
| 2000 | 31.3 |
| 2001 | 33.64 |
| 2002 | 31.87 |
| 2003 | 30.82 |
| 2004 | 28.87 |
| 2005 | 30.61 |
| 2006 | 28.83 |
| 2007 | 29.68 |
| 2008 | 27.29 |
| 2009 | |
| 2010 | 24.84 |
| 2011 | 24.11 |
| 2012 | 23.04 |
| 2013 | 22.41 |
| 2014 | 21.68 |
| 2015 | 21.76 |
| 2016 | 20.87 |
| 2017 | |
| 2018 | 16.38 |