| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.62 | 65 |
| 2015 | 6.41 | 63 |
| 2014 | 6.26 | 61 |
| 2013 | 6.15 | 56 |
| 2012 | 6.07 | 51 |
| 2011 | 6 | 49 |
| 2010 | 5.93 | 47 |
| 2009 | 5.87 | 46 |
| 2008 | 5.82 | 43 |
| 2007 | 5.78 | 41 |
| 2006 | 5.74 | 39 |
| 2005 | 5.69 | 39 |
| 2004 | 5.66 | 36 |
| 2003 | 5.63 | 32 |
| 2002 | 5.6 | 29 |
| 2001 | 5.58 | 31 |
| 2000 | 5.57 | 30 |
| 1999 | 5.69 | 34 |
| 1998 | 5.82 | 40 |
| 1997 | 5.93 | 44 |
| 1996 | 5.99 | 45 |
| 1995 | 6.01 | 48 |
| 1994 | 5.95 | 45 |
| 1993 | 5.85 | 42 |
| 1992 | 5.73 | 37 |
| 1991 | 5.61 | 35 |
| 1990 | 5.49 | 30 |
| 1989 | 5.42 | 26 |
| 1988 | 5.36 | 25 |
| 1987 | 5.3 | 25 |
| 1986 | 5.23 | 22 |