| 年度 | 实际值 |
|---|---|
| 1995 | 31.2 |
| 1996 | 30.6 |
| 1997 | 27.92 |
| 1998 | 26.5 |
| 1999 | 25.6 |
| 2000 | 23.8 |
| 2001 | 22.57 |
| 2002 | 21.96 |
| 2003 | 20.53 |
| 2004 | 20.59 |
| 2005 | 20.36 |
| 2006 | 18.7 |
| 2007 | 18.88 |
| 2008 | 18.62 |
| 2009 | |
| 2010 | 16.54 |
| 2011 | 15.63 |
| 2012 | 15.16 |
| 2013 | 13.94 |
| 2014 | 13.15 |
| 2015 | 12.97 |
| 2016 | 12.53 |
| 2017 | |
| 2018 | 10.99 |