| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.9 | 84 |
| 2015 | 7.73 | 84 |
| 2014 | 7.61 | 83 |
| 2013 | 7.49 | 80 |
| 2012 | 7.37 | 76 |
| 2011 | 7.29 | 77 |
| 2010 | 7.26 | 78 |
| 2009 | 7.14 | 76 |
| 2008 | 7.1 | 76 |
| 2007 | 7.08 | 76 |
| 2006 | 7.05 | 75 |
| 2005 | 6.97 | 75 |
| 2004 | 7.02 | 75 |
| 2003 | 6.99 | 75 |
| 2002 | 6.91 | 75 |
| 2001 | 6.82 | 73 |
| 2000 | 6.74 | 74 |
| 1999 | 6.69 | 69 |
| 1998 | 6.65 | 66 |
| 1997 | 6.59 | 64 |
| 1996 | 6.53 | 64 |
| 1995 | 6.45 | 62 |
| 1994 | 6.52 | 62 |
| 1993 | 6.57 | 65 |
| 1992 | 6.61 | 66 |
| 1991 | 6.61 | 70 |
| 1990 | 6.57 | 70 |
| 1989 | 6.47 | 65 |
| 1988 | 6.49 | 68 |
| 1987 | 6.67 | 75 |
| 1986 | 6.97 | 85 |