| 年度 | 实际值 |
|---|---|
| 1993 | 22.8 |
| 1994 | |
| 1995 | 25.1 |
| 1996 | 25.1 |
| 1997 | |
| 1998 | |
| 1999 | |
| 2000 | 28.8 |
| 2001 | 1.80666666666667 |
| 2002 | |
| 2003 | 25.72 |
| 2004 | 27.03 |
| 2005 | 27 |
| 2006 | 29.55 |
| 2007 | 36.9 |
| 2008 | 39.67 |
| 2009 | |
| 2010 | 37.93 |
| 2011 | 38.16 |
| 2012 | 43.45 |
| 2013 | 43.76 |
| 2014 | 43.8 |
| 2015 | 41.76 |
| 2016 | 38.33 |
| 2017 | 38.22 |
| 2018 | 38.57 |