| 年度 | 实际值 |
|---|---|
| 1995 | 34.7 |
| 1996 | 34.9 |
| 1997 | 27.96 |
| 1998 | 26.7 |
| 1999 | 25.2 |
| 2000 | 24.7 |
| 2001 | 23.7 |
| 2002 | 22.05 |
| 2003 | 20.32 |
| 2004 | 20.74 |
| 2005 | 18.31 |
| 2006 | 17.45 |
| 2007 | 18.29 |
| 2008 | 16.62 |
| 2009 | |
| 2010 | 13.45 |
| 2011 | 12.48 |
| 2012 | 11.92 |
| 2013 | 11.54 |
| 2014 | 11.19 |
| 2015 | 10.95 |
| 2016 | 10.9 |
| 2017 | |
| 2018 | 10.27 |