| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 8.37 | 14 |
| 2015 | 8.75 | 21 |
| 2014 | 7.89 | 21 |
| 2013 | 5.79 | 43 |
| 2012 | 3.08 | 77 |
| 2011 | 6.74 | 35 |
| 2010 | 6.83 | 32 |
| 2009 | 6.1 | 58 |
| 2008 | 3.19 | 90 |
| 2007 | 3.06 | 92 |
| 2006 | 8.15 | 36 |
| 2005 | 9.79 | 28 |
| 2004 | 9.76 | 17 |
| 2003 | 8.54 | 22 |
| 2002 | 9.27 | 24 |
| 2001 | 5.7 | 45 |
| 2000 | 3.69 | 55 |
| 1999 | 2.79 | 68 |
| 1998 | 3.05 | 65 |
| 1997 | 4.84 | 40 |
| 1996 | -.82 | 106 |
| 1995 | 2.3 | 61 |
| 1994 | 3.33 | 45 |
| 1993 | 11.7 | 13 |
| 1992 | 10.9 | 15 |
| 1991 | 2.08 | 68 |
| 1990 | 0.42 | 68 |
| 1989 | 0.64 | 72 |
| 1988 | 0.78 | 63 |
| 1987 | 2.05 | 54 |
| 1986 | 7.92 | 20 |