| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 11.36 | 18 |
| 2014 | 12.15 | 12 |
| 2013 | 11.23 | 16 |
| 2012 | 10.64 | 24 |
| 2011 | 5.71 | 57 |
| 2010 | 8.42 | 37 |
| 2009 | 6.62 | 48 |
| 2008 | 11.68 | 30 |
| 2007 | 25.97 | 9 |
| 2006 | 31.23 | 5 |
| 2005 | 21.77 | 10 |
| 2004 | 8.8 | 26 |
| 2003 | 19.56 | 7 |
| 2002 | 8.13 | 16 |
| 2001 | 12.37 | 11 |
| 2000 | 5.22 | 49 |
| 1999 | 6.76 | 34 |
| 1998 | 3.13 | 75 |
| 1997 | 3.37 | 58 |
| 1996 | 3.05 | 44 |
| 1995 | 5.45 | 23 |
| 1994 | 4.21 | 24 |
| 1993 | 2.85 | 29 |
| 1992 | 3.94 | 20 |
| 1991 | 11.37 | 4 |
| 1990 | 13.19 | 4 |
| 1989 | 9.82 | 4 |
| 1988 | 8.27 | 4 |
| 1987 | 11.45 | 3 |
| 1986 | 7.78 | 2 |