| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 6.69 | 93 |
| 2014 | 7.12 | 94 |
| 2013 | 6.87 | 99 |
| 2012 | 8.68 | 87 |
| 2011 | 8.9 | 87 |
| 2010 | 9.27 | 85 |
| 2009 | 8.96 | 89 |
| 2008 | 8.23 | 90 |
| 2007 | 9.22 | 87 |
| 2006 | 10.47 | 78 |
| 2005 | 11.33 | 77 |
| 2004 | 9.74 | 91 |
| 2003 | 10.94 | 84 |
| 2002 | 10.94 | 82 |
| 2001 | 10.51 | 84 |
| 2000 | 11.82 | 80 |
| 1999 | 9.92 | 87 |
| 1998 | 9.62 | 91 |
| 1997 | 9.53 | 90 |
| 1996 | 10.42 | 89 |
| 1995 | 10.61 | 89 |
| 1994 | 11.27 | 83 |
| 1993 | 8.27 | 96 |
| 1992 | 7.7 | 97 |
| 1991 | 10.74 | 85 |
| 1990 | 9.79 | 88 |
| 1989 | 9.12 | 85 |
| 1988 | 9.81 | 82 |
| 1987 | 9.68 | 82 |
| 1986 | 8.23 | 79 |