| 年度 | 实际值 |
|---|---|
| 1993 | 25.3 |
| 1994 | |
| 1995 | 13.5 |
| 1996 | 12.5 |
| 1997 | 11.3 |
| 1998 | 22.3 |
| 1999 | 24 |
| 2000 | 25.7 |
| 2001 | 2.24666666666667 |
| 2002 | |
| 2003 | 35.77 |
| 2004 | 36.06 |
| 2005 | |
| 2006 | 34.9 |
| 2007 | 33.95 |
| 2008 | 35.32 |
| 2009 | |
| 2010 | 29.05 |
| 2011 | 29.45 |
| 2012 | 34.7 |
| 2013 | 31.03 |
| 2014 | 31 |
| 2015 | 30.66 |
| 2016 | 39.48 |
| 2017 | 39.35 |
| 2018 | 38.51 |