| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.46 | 78 |
| 2015 | 7.41 | 77 |
| 2014 | 7.43 | 77 |
| 2013 | 7.45 | 77 |
| 2012 | 7.47 | 80 |
| 2011 | 7.5 | 82 |
| 2010 | 7.55 | 86 |
| 2009 | 7.62 | 88 |
| 2008 | 7.73 | 89 |
| 2007 | 7.87 | 89 |
| 2006 | 8 | 93 |
| 2005 | 8.1 | 94 |
| 2004 | 8.21 | 94 |
| 2003 | 8.29 | 94 |
| 2002 | 8.32 | 95 |
| 2001 | 8.31 | 96 |
| 2000 | 8.28 | 97 |
| 1999 | 8.29 | 100 |
| 1998 | 8.24 | 101 |
| 1997 | 8.16 | 102 |
| 1996 | 8.06 | 101 |
| 1995 | 7.95 | 102 |
| 1994 | 7.97 | 103 |
| 1993 | 8.02 | 104 |
| 1992 | 8.09 | 111 |
| 1991 | 8.14 | 114 |
| 1990 | 8.16 | 116 |
| 1989 | 8.16 | 115 |
| 1988 | 8.14 | 115 |
| 1987 | 8.1 | 116 |
| 1986 | 8.05 | 115 |