| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 1.83 | 10 |
| 2015 | 1.69 | 10 |
| 2014 | 2.8 | 21 |
| 2013 | 2.8 | 18 |
| 2012 | 2.8 | 21 |
| 2011 | 2.9 | 18 |
| 2010 | 3.1 | 23 |
| 2009 | 4.3 | 39 |
| 2008 | 3.96 | 42 |
| 2007 | 3.9 | 42 |
| 2006 | 4.48 | 49 |
| 2005 | 5.59 | 60 |
| 2004 | 5.84 | 63 |
| 2003 | 5.93 | 61 |
| 2002 | 5.65 | 57 |
| 2001 | 3.76 | 33 |
| 2000 | 3.7 | 34 |
| 1999 | 4.85 | 47 |
| 1998 | 3.41 | 30 |
| 1997 | 2.5 | 19 |
| 1996 | 3.57 | 30 |
| 1995 | 3.3 | 30 |
| 1994 | 3.03 | 27 |
| 1993 | 3.07 | 29 |
| 1992 | 3.09 | 28 |
| 1991 | 1.9 | 16 |