| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.73 | 81 |
| 2015 | 7.56 | 81 |
| 2014 | 7.37 | 81 |
| 2013 | 7.21 | 81 |
| 2012 | 7.05 | 82 |
| 2011 | 6.9 | 82 |
| 2010 | 6.76 | 82 |
| 2009 | 6.61 | 84 |
| 2008 | 6.47 | 85 |
| 2007 | 6.34 | 86 |
| 2006 | 6.21 | 86 |
| 2005 | 6.08 | 86 |
| 2004 | 5.95 | 87 |
| 2003 | 5.84 | 87 |
| 2002 | 5.72 | 87 |
| 2001 | 5.62 | 86 |
| 2000 | 5.52 | 85 |
| 1999 | 5.42 | 86 |
| 1998 | 5.34 | 87 |
| 1997 | 5.26 | 87 |
| 1996 | 5.18 | 87 |
| 1995 | 5.1 | 85 |
| 1994 | 5.02 | 85 |
| 1993 | 4.95 | 84 |
| 1992 | 4.88 | 81 |
| 1991 | 4.82 | 80 |
| 1990 | 4.75 | 79 |
| 1989 | 4.69 | 79 |
| 1988 | 4.63 | 79 |
| 1987 | 4.57 | 79 |
| 1986 | 4.51 | 81 |