| 年度 | 实际值 |
|---|---|
| 1992 | 10.7 |
| 1993 | 10.4 |
| 1994 | |
| 1995 | 7.92 |
| 1996 | 2.59 |
| 1997 | 4.71 |
| 1998 | 5.47 |
| 1999 | 3.04 |
| 2000 | 3.68 |
| 2001 | 5.1 |
| 2002 | 4.87 |
| 2003 | 4.37 |
| 2004 | 5.71 |
| 2005 | 5.47 |
| 2006 | 7.36 |
| 2007 | 8.28 |
| 2008 | 10.03 |
| 2009 | |
| 2010 | 4.23 |
| 2011 | 7.4 |
| 2012 | 11 |
| 2013 | 11.2 |
| 2014 | 11.3 |
| 2015 | 13.07 |
| 2016 | 16.14 |
| 2017 | 17.83 |
| 2018 | 15.27 |