| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.71 | 12 |
| 2015 | 7.45 | 36 |
| 2014 | 7.44 | 37 |
| 2013 | 7.43 | 31 |
| 2012 | 7.29 | 47 |
| 2011 | 9.58 | 32 |
| 2010 | 5.59 | 55 |
| 2009 | 5.23 | 60 |
| 2008 | 7.38 | 60 |
| 2007 | 5.14 | 96 |
| 2006 | 4.24 | 97 |
| 2005 | 3.81 | 85 |
| 2004 | 4.31 | 63 |
| 2003 | 3.78 | 57 |
| 2002 | 3.9 | 61 |
| 2001 | 2.82 | 82 |
| 2000 | 5.22 | 50 |
| 1999 | 6.95 | 32 |
| 1998 | 4.71 | 46 |
| 1997 | 4.63 | 40 |
| 1996 | 2.79 | 48 |
| 1995 | 2.15 | 63 |
| 1994 | 1.21 | 79 |
| 1993 | 2.21 | 36 |
| 1992 | 0.84 | 73 |
| 1991 | 2.82 | 29 |
| 1990 | 0.07 | 118 |
| 1989 | 0.28 | 95 |
| 1988 | 0 | 124 |
| 1987 | 0.06 | 106 |
| 1986 | 0 | 111 |