| 年度 | 实际值 |
|---|---|
| 1995 | 38.4 |
| 1996 | 39.7 |
| 1997 | 21.7 |
| 1998 | 39.8 |
| 1999 | 36 |
| 2000 | 35.4 |
| 2001 | 33.47 |
| 2002 | 32.82 |
| 2003 | 31.14 |
| 2004 | 31.3 |
| 2005 | 32.67 |
| 2006 | 29.64 |
| 2007 | 29.34 |
| 2008 | 27.05 |
| 2009 | |
| 2010 | 23.68 |
| 2011 | 22.51 |
| 2012 | 21.71 |
| 2013 | 18.27 |
| 2014 | 17.08 |
| 2015 | 14.89 |
| 2016 | 13.93 |
| 2017 | 13.4 |
| 2018 | 12.35 |