| 年度 | 实际值 |
|---|---|
| 1995 | 16.5 |
| 1996 | 29.8 |
| 1997 | 27.13 |
| 1998 | 27.4 |
| 1999 | 23.1 |
| 2000 | 22.1 |
| 2001 | 20.57 |
| 2002 | 23.29 |
| 2003 | 22.51 |
| 2004 | 23.38 |
| 2005 | 22.2 |
| 2006 | 22.55 |
| 2007 | 23.1 |
| 2008 | 24.86 |
| 2009 | |
| 2010 | 21.66 |
| 2011 | 21.98 |
| 2012 | 21.13 |
| 2013 | 20.15 |
| 2014 | 18.56 |
| 2015 | 17.99 |
| 2016 | 17.79 |
| 2017 | |
| 2018 | 13.96 |