| 年度 | 实际值 |
|---|---|
| 1993 | 8.1 |
| 1994 | |
| 1995 | 8.7 |
| 1996 | 3.9 |
| 1997 | 4.3 |
| 1998 | 4.5 |
| 1999 | 4.9 |
| 2000 | 5.5 |
| 2001 | .813333333333333 |
| 2002 | |
| 2003 | 10.83 |
| 2004 | 2.08 |
| 2005 | 33 |
| 2006 | 24.62 |
| 2007 | 20.85 |
| 2008 | 23.4 |
| 2009 | |
| 2010 | 35.4 |
| 2011 | 36.48 |
| 2012 | 33.67 |
| 2013 | 34.54 |
| 2014 | 35.54 |
| 2015 | 38.11 |
| 2016 | 38.43 |
| 2017 | 38.68 |
| 2018 | 38.95 |