| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 9.27 | 94 |
| 2015 | 8.96 | 94 |
| 2014 | 8.69 | 94 |
| 2013 | 8.49 | 93 |
| 2012 | 8.34 | 93 |
| 2011 | 8.23 | 92 |
| 2010 | 8.12 | 91 |
| 2009 | 7.96 | 91 |
| 2008 | 7.82 | 90 |
| 2007 | 7.7 | 86 |
| 2006 | 7.59 | 84 |
| 2005 | 7.49 | 84 |
| 2004 | 7.4 | 83 |
| 2003 | 7.31 | 81 |
| 2002 | 7.23 | 81 |
| 2001 | 7.15 | 80 |
| 2000 | 7.06 | 80 |
| 1999 | 6.93 | 78 |
| 1998 | 6.79 | 72 |
| 1997 | 6.67 | 66 |
| 1996 | 6.55 | 65 |
| 1995 | 6.45 | 61 |
| 1994 | 6.41 | 61 |
| 1993 | 6.38 | 58 |
| 1992 | 6.35 | 59 |
| 1991 | 6.34 | 60 |
| 1990 | 6.34 | 64 |
| 1989 | 6.37 | 61 |
| 1988 | 6.43 | 63 |
| 1987 | 6.5 | 68 |
| 1986 | 6.57 | 74 |