| 年度 | 实际值 |
|---|---|
| 1995 | 3.6 |
| 1996 | 3.7 |
| 1997 | 17.14 |
| 1998 | 22.7 |
| 1999 | 20.5 |
| 2000 | 19.1 |
| 2001 | 12.2 |
| 2002 | 15.75 |
| 2003 | 13.17 |
| 2004 | 15.46 |
| 2005 | 15.41 |
| 2006 | 14.77 |
| 2007 | 13.71 |
| 2008 | 13.86 |
| 2009 | |
| 2010 | 13.85 |
| 2011 | 14.62 |
| 2012 | 16.51 |
| 2013 | 15.65 |
| 2014 | 14.71 |
| 2015 | 14.71 |
| 2016 | 13.18 |
| 2017 | 12.26 |
| 2018 | 11.94 |