| 年度 | 实际值 |
|---|---|
| 1993 | 34 |
| 1994 | |
| 1995 | 34.8 |
| 1996 | 35.2 |
| 1997 | 35.2 |
| 1998 | 31.7 |
| 1999 | 32.2 |
| 2000 | 33.3 |
| 2001 | 2.30666666666667 |
| 2002 | |
| 2003 | 39.57 |
| 2004 | 39.67 |
| 2005 | 44 |
| 2006 | 41.93 |
| 2007 | 41.17 |
| 2008 | 38.5 |
| 2009 | |
| 2010 | 42.52 |
| 2011 | 37.36 |
| 2012 | 35.26 |
| 2013 | 35.85 |
| 2014 | 35.41 |
| 2015 | 41.27 |
| 2016 | 42.41 |
| 2017 | 43.06 |
| 2018 | 41.49 |