| 年度 | 实际值 |
|---|---|
| 1993 | 29.7 |
| 1994 | |
| 1995 | 30 |
| 1996 | 30.3 |
| 1997 | 30.8 |
| 1998 | 31.9 |
| 1999 | 32 |
| 2000 | 32 |
| 2001 | 2.14 |
| 2002 | |
| 2003 | 33.4 |
| 2004 | 33.7 |
| 2005 | 37 |
| 2006 | 35.98 |
| 2007 | 37.66 |
| 2008 | 38.68 |
| 2009 | |
| 2010 | 39.6 |
| 2011 | 40.3 |
| 2012 | 40.33 |
| 2013 | 40.01 |
| 2014 | 40.8 |
| 2015 | 40.83 |
| 2016 | 41.99 |
| 2017 | 41.91 |
| 2018 | 41.91 |