| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 9.8 | 98 |
| 2015 | 9.55 | 97 |
| 2014 | 9.31 | 97 |
| 2013 | 9.09 | 96 |
| 2012 | 8.88 | 95 |
| 2011 | 8.68 | 96 |
| 2010 | 8.49 | 95 |
| 2009 | 8.31 | 93 |
| 2008 | 8.14 | 93 |
| 2007 | 7.99 | 91 |
| 2006 | 7.84 | 91 |
| 2005 | 7.7 | 88 |
| 2004 | 7.56 | 87 |
| 2003 | 7.43 | 85 |
| 2002 | 7.31 | 82 |
| 2001 | 7.19 | 82 |
| 2000 | 7.06 | 81 |
| 1999 | 6.96 | 80 |
| 1998 | 6.87 | 76 |
| 1997 | 6.77 | 72 |
| 1996 | 6.67 | 67 |
| 1995 | 6.57 | 66 |
| 1994 | 6.53 | 63 |
| 1993 | 6.48 | 62 |
| 1992 | 6.43 | 61 |
| 1991 | 6.37 | 63 |
| 1990 | 6.3 | 61 |
| 1989 | 6.26 | 58 |
| 1988 | 6.2 | 55 |
| 1987 | 6.15 | 56 |
| 1986 | 6.08 | 54 |