| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.26 | 56 |
| 2015 | 6.25 | 59 |
| 2014 | 6.22 | 58 |
| 2013 | 6.2 | 59 |
| 2012 | 6.19 | 60 |
| 2011 | 6.18 | 60 |
| 2010 | 6.18 | 59 |
| 2009 | 6.09 | 53 |
| 2008 | 6 | 49 |
| 2007 | 5.91 | 47 |
| 2006 | 5.82 | 44 |
| 2005 | 5.73 | 42 |
| 2004 | 5.65 | 35 |
| 2003 | 5.57 | 29 |
| 2002 | 5.49 | 27 |
| 2001 | 5.41 | 24 |
| 2000 | 5.33 | 23 |
| 1999 | 5.3 | 20 |
| 1998 | 5.27 | 19 |
| 1997 | 5.25 | 20 |
| 1996 | 5.22 | 19 |
| 1995 | 5.19 | 18 |
| 1994 | 5.31 | 20 |
| 1993 | 5.48 | 27 |
| 1992 | 5.69 | 35 |
| 1991 | 5.96 | 47 |
| 1990 | 6.26 | 58 |
| 1989 | 6.41 | 64 |
| 1988 | 6.57 | 72 |
| 1987 | 6.74 | 79 |
| 1986 | 6.93 | 84 |