| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.69 | 82 |
| 2015 | 7.69 | 83 |
| 2014 | 7.7 | 85 |
| 2013 | 7.67 | 85 |
| 2012 | 7.61 | 84 |
| 2011 | 7.52 | 83 |
| 2010 | 7.42 | 82 |
| 2009 | 7.37 | 81 |
| 2008 | 7.3 | 79 |
| 2007 | 7.2 | 78 |
| 2006 | 7.08 | 77 |
| 2005 | 6.95 | 74 |
| 2004 | 6.86 | 72 |
| 2003 | 6.78 | 71 |
| 2002 | 6.69 | 70 |
| 2001 | 6.59 | 68 |
| 2000 | 6.48 | 63 |
| 1999 | 6.38 | 58 |
| 1998 | 6.28 | 57 |
| 1997 | 6.18 | 53 |
| 1996 | 6.06 | 49 |
| 1995 | 5.94 | 44 |
| 1994 | 5.91 | 42 |
| 1993 | 5.88 | 43 |
| 1992 | 5.84 | 43 |
| 1991 | 5.79 | 43 |
| 1990 | 5.73 | 43 |
| 1989 | 5.73 | 42 |
| 1988 | 5.73 | 40 |
| 1987 | 5.71 | 38 |
| 1986 | 5.68 | 35 |