| 年度 | 实际值 |
|---|---|
| 1993 | 9.3 |
| 1994 | |
| 1995 | 17.5 |
| 1996 | 15.2 |
| 1997 | |
| 1998 | |
| 1999 | |
| 2000 | 18.1 |
| 2001 | 1.20666666666667 |
| 2002 | |
| 2003 | 19.44 |
| 2004 | 20.42 |
| 2005 | 23 |
| 2006 | 22.83 |
| 2007 | 22.62 |
| 2008 | 29.11 |
| 2009 | |
| 2010 | 33.53 |
| 2011 | 38.58 |
| 2012 | 38.78 |
| 2013 | 39.21 |
| 2014 | 38.84 |
| 2015 | 38.84 |
| 2016 | 37.57 |
| 2017 | 36.82 |
| 2018 | 36.11 |