| 年度 | 实际值 |
|---|---|
| 1993 | 34.7 |
| 1994 | |
| 1995 | 30.9 |
| 1996 | 29.5 |
| 1997 | |
| 1998 | |
| 1999 | 27.2 |
| 2000 | 28.8 |
| 2001 | 1.74666666666667 |
| 2002 | |
| 2003 | 27.66 |
| 2004 | 26.5 |
| 2005 | 25 |
| 2006 | 28.6 |
| 2007 | 40.02 |
| 2008 | 36.85 |
| 2009 | |
| 2010 | 38.19 |
| 2011 | 41.65 |
| 2012 | 40.61 |
| 2013 | 38.65 |
| 2014 | 39.88 |
| 2015 | 40.09 |
| 2016 | 40.46 |
| 2017 | 47.03 |
| 2018 | 49.84 |