| 年度 | 实际值 |
|---|---|
| 1995 | 29.5 |
| 1996 | 26.2 |
| 1997 | 23.43 |
| 1998 | 24.2 |
| 1999 | 21.7 |
| 2000 | 23.5 |
| 2001 | 23.5 |
| 2002 | 22.91 |
| 2003 | 22.92 |
| 2004 | 22.6 |
| 2005 | 20.79 |
| 2006 | 19.1 |
| 2007 | 19.12 |
| 2008 | 19.05 |
| 2009 | |
| 2010 | 15.74 |
| 2011 | 14.86 |
| 2012 | 14.43 |
| 2013 | 14.25 |
| 2014 | 13.75 |
| 2015 | 13.12 |
| 2016 | 12.54 |
| 2017 | |
| 2018 | 10.43 |