| 年度 | 实际值 |
|---|---|
| 1993 | 29.2 |
| 1994 | |
| 1995 | 31.1 |
| 1996 | 31.3 |
| 1997 | 31.2 |
| 1998 | 31.6 |
| 1999 | 31.8 |
| 2000 | 32.3 |
| 2001 | 2.29333333333333 |
| 2002 | |
| 2003 | 32.89 |
| 2004 | 31.9 |
| 2005 | 33 |
| 2006 | 36.15 |
| 2007 | 37.01 |
| 2008 | 39.26 |
| 2009 | |
| 2010 | 41.53 |
| 2011 | 47.22 |
| 2012 | 41.06 |
| 2013 | 42.89 |
| 2014 | 48.98 |
| 2015 | 44.42 |
| 2016 | 45.45 |
| 2017 | 44.42 |
| 2018 | 41.16 |