| 年度 | 实际值 |
|---|---|
| 1993 | 5.5 |
| 1994 | |
| 1995 | 20.2 |
| 1996 | 17.6 |
| 1997 | 17.6 |
| 1998 | 17.7 |
| 1999 | 18.5 |
| 2000 | 20.3 |
| 2001 | 1.35333333333333 |
| 2002 | |
| 2003 | 22.19 |
| 2004 | 22.24 |
| 2005 | 23 |
| 2006 | 23.13 |
| 2007 | 23.89 |
| 2008 | 25.27 |
| 2009 | |
| 2010 | 26.01 |
| 2011 | 25.39 |
| 2012 | 27.99 |
| 2013 | 29.27 |
| 2014 | 1.02 |
| 2015 | |
| 2016 | 30.54 |
| 2017 | 31.45 |
| 2018 | 31.8 |