| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 3.88 | 30 |
| 2015 | 2.68 | 70 |
| 2014 | 1.64 | 108 |
| 2013 | 1.22 | 129 |
| 2012 | 1.75 | 106 |
| 2011 | 3.02 | 66 |
| 2010 | 4.64 | 21 |
| 2009 | 6.16 | 5 |
| 2008 | 7.35 | 3 |
| 2007 | 7.8 | 4 |
| 2006 | 7.52 | 3 |
| 2005 | 6.92 | 3 |
| 2004 | 6.37 | 7 |
| 2003 | 5.76 | 11 |
| 2002 | 5.25 | 13 |
| 2001 | 4.83 | 17 |
| 2000 | 4.31 | 26 |
| 1999 | 3.65 | 51 |
| 1998 | 3.1 | 68 |
| 1997 | 2.77 | 78 |
| 1996 | 2.62 | 87 |
| 1995 | 2.53 | 89 |
| 1994 | 2.46 | 96 |
| 1993 | 2.47 | 102 |
| 1992 | 2.66 | 94 |
| 1991 | 2.97 | 86 |
| 1990 | 3.26 | 86 |
| 1989 | 3.58 | 75 |
| 1988 | 3.78 | 78 |
| 1987 | 3.74 | 86 |
| 1986 | 3.53 | 88 |