| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.45 | 32 |
| 2015 | 5.61 | 37 |
| 2014 | 5.84 | 43 |
| 2013 | 6.1 | 53 |
| 2012 | 6.37 | 65 |
| 2011 | 6.66 | 70 |
| 2010 | 6.96 | 76 |
| 2009 | 7.29 | 79 |
| 2008 | 7.62 | 86 |
| 2007 | 7.95 | 90 |
| 2006 | 8.24 | 95 |
| 2005 | 8.5 | 95 |
| 2004 | 8.74 | 98 |
| 2003 | 8.93 | 102 |
| 2002 | 9.06 | 104 |
| 2001 | 9.16 | 110 |
| 2000 | 9.22 | 111 |
| 1999 | 9.28 | 114 |
| 1998 | 9.3 | 116 |
| 1997 | 9.33 | 116 |
| 1996 | 9.36 | 118 |
| 1995 | 9.4 | 121 |
| 1994 | 9.5 | 121 |
| 1993 | 9.63 | 122 |
| 1992 | 9.76 | 124 |
| 1991 | 9.86 | 128 |
| 1990 | 9.89 | 132 |
| 1989 | 9.94 | 131 |
| 1988 | 9.93 | 130 |
| 1987 | 9.88 | 131 |
| 1986 | 9.82 | 131 |