| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.98 | 86 |
| 2015 | 6.83 | 86 |
| 2014 | 6.68 | 87 |
| 2013 | 6.54 | 87 |
| 2012 | 6.42 | 88 |
| 2011 | 6.31 | 88 |
| 2010 | 6.2 | 89 |
| 2009 | 6.08 | 89 |
| 2008 | 5.97 | 91 |
| 2007 | 5.87 | 91 |
| 2006 | 5.77 | 91 |
| 2005 | 5.67 | 93 |
| 2004 | 5.51 | 95 |
| 2003 | 5.36 | 95 |
| 2002 | 5.2 | 95 |
| 2001 | 5.04 | 98 |
| 2000 | 4.88 | 99 |
| 1999 | 4.78 | 100 |
| 1998 | 4.67 | 100 |
| 1997 | 4.56 | 101 |
| 1996 | 4.45 | 103 |
| 1995 | 4.35 | 104 |
| 1994 | 4.27 | 105 |
| 1993 | 4.19 | 106 |
| 1992 | 4.12 | 106 |
| 1991 | 4.05 | 107 |
| 1990 | 3.99 | 107 |
| 1989 | 3.94 | 106 |
| 1988 | 3.9 | 107 |
| 1987 | 3.86 | 111 |
| 1986 | 3.82 | 112 |