| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 2.91 | 23 |
| 2015 | 2.91 | 23 |
| 2014 | 2.7 | 19 |
| 2013 | 3.29 | 27 |
| 2012 | 3.46 | 32 |
| 2011 | 3.2 | 22 |
| 2010 | 2.5 | 14 |
| 2009 | 1.67 | 11 |
| 2008 | 1.6 | 10 |
| 2007 | 1.8 | 12 |
| 2006 | 1.9 | 13 |
| 2005 | 1.9 | 10 |
| 2004 | 1.9 | 8 |
| 2003 | 2.3 | 14 |
| 2002 | 3.3 | 28 |
| 2001 | 4.1 | 40 |
| 2000 | 5.4 | 58 |
| 1999 | 6.3 | 67 |
| 1998 | 6.2 | 64 |
| 1997 | 7.1 | 86 |
| 1996 | 7.6 | 89 |
| 1995 | 8.3 | 97 |
| 1994 | 4.34 | 45 |
| 1993 | 3.71 | 37 |
| 1992 | 3.71 | 40 |
| 1991 | 3.74 | 45 |