| 年度 | 实际值 |
|---|---|
| 1993 | 31.9 |
| 1994 | |
| 1995 | 28 |
| 1996 | 28 |
| 1997 | 28.4 |
| 1998 | 28 |
| 1999 | 28.3 |
| 2000 | 28.2 |
| 2001 | 1.88666666666667 |
| 2002 | |
| 2003 | 36.84 |
| 2004 | 36.29 |
| 2005 | 36 |
| 2006 | 38.04 |
| 2007 | 36.3 |
| 2008 | 36.29 |
| 2009 | |
| 2010 | 37.37 |
| 2011 | 33.45 |
| 2012 | 33.95 |
| 2013 | 34.37 |
| 2014 | 35.16 |
| 2015 | 33.73 |
| 2016 | 34.47 |
| 2017 | |
| 2018 | 41.49 |