| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 39.8 | 41 |
| 2015 | 40.1 | 41 |
| 2014 | 40.5 | 39 |
| 2013 | 40.9 | 39 |
| 2012 | 41.4 | 38 |
| 2011 | 41.9 | 36 |
| 2010 | 42.4 | 34 |
| 2009 | 43 | 32 |
| 2008 | 43.6 | 28 |
| 2007 | 44.3 | 22 |
| 2006 | 44.9 | 19 |
| 2005 | 45.6 | 18 |
| 2004 | 46.1 | 16 |
| 2003 | 46.6 | 14 |
| 2002 | 47.1 | 10 |
| 2001 | 47.4 | 9 |
| 2000 | 47.8 | 8 |
| 1999 | 48.1 | 8 |
| 1998 | 48.4 | 5 |
| 1997 | 48.5 | 5 |
| 1996 | 48.6 | 4 |
| 1995 | 48.6 | 4 |
| 1994 | 48.6 | 4 |
| 1993 | 48.6 | 4 |
| 1992 | 48.6 | 3 |
| 1991 | 48.6 | 4 |
| 1990 | 48.6 | 4 |