| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.75 | 83 |
| 2015 | 7.6 | 81 |
| 2014 | 7.52 | 80 |
| 2013 | 7.47 | 78 |
| 2012 | 7.42 | 78 |
| 2011 | 7.38 | 79 |
| 2010 | 7.33 | 80 |
| 2009 | 7.39 | 82 |
| 2008 | 7.42 | 80 |
| 2007 | 7.42 | 80 |
| 2006 | 7.4 | 81 |
| 2005 | 7.35 | 81 |
| 2004 | 7.4 | 82 |
| 2003 | 7.42 | 84 |
| 2002 | 7.41 | 85 |
| 2001 | 7.36 | 86 |
| 2000 | 7.29 | 85 |
| 1999 | 7.17 | 82 |
| 1998 | 7.05 | 80 |
| 1997 | 6.93 | 77 |
| 1996 | 6.81 | 75 |
| 1995 | 6.68 | 70 |
| 1994 | 6.61 | 66 |
| 1993 | 6.54 | 64 |
| 1992 | 6.47 | 62 |
| 1991 | 6.4 | 64 |
| 1990 | 6.33 | 62 |
| 1989 | 6.32 | 60 |
| 1988 | 6.32 | 61 |
| 1987 | 6.33 | 61 |
| 1986 | 6.34 | 65 |