| 年度 | 实际值 |
|---|---|
| 1995 | 29.6 |
| 1996 | 27.2 |
| 1997 | 7.45 |
| 1998 | 28.8 |
| 1999 | 19.8 |
| 2000 | 19.6 |
| 2001 | 30.71 |
| 2002 | 29.6 |
| 2003 | 22.47 |
| 2004 | 17.5 |
| 2005 | 18.42 |
| 2006 | 17.48 |
| 2007 | 17.18 |
| 2008 | 17.91 |
| 2009 | |
| 2010 | 15.23 |
| 2011 | 13.3 |
| 2012 | 12.07 |
| 2013 | 11.5 |
| 2014 | 11.05 |
| 2015 | 11.1 |
| 2016 | 10.82 |
| 2017 | 8.47 |
| 2018 | 8.17 |