| 年度 | 实际值 |
|---|---|
| 1995 | 3.5 |
| 1996 | 3.6 |
| 1997 | 22.38 |
| 1998 | 32.4 |
| 1999 | 32.4 |
| 2000 | 30 |
| 2001 | 28.98 |
| 2002 | 27.97 |
| 2003 | 18.43 |
| 2004 | 24.15 |
| 2005 | 22.68 |
| 2006 | 21.54 |
| 2007 | 19.67 |
| 2008 | 19.36 |
| 2009 | |
| 2010 | 21.05 |
| 2011 | 18.45 |
| 2012 | 17.13 |
| 2013 | 17.59 |
| 2014 | 17.98 |
| 2015 | 17.27 |
| 2016 | 16.23 |
| 2017 | 14.01 |
| 2018 | 12.88 |