| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.33 | 76 |
| 2015 | 8.9 | 78 |
| 2014 | 7.07 | 95 |
| 2013 | 5.56 | 104 |
| 2012 | 5.6 | 103 |
| 2011 | 5.18 | 108 |
| 2010 | 5.23 | 107 |
| 2009 | 5.28 | 109 |
| 2008 | 4.34 | 119 |
| 2007 | 4.13 | 118 |
| 2006 | 4.53 | 116 |
| 2005 | 3.43 | 129 |
| 2004 | 5.77 | 111 |
| 2003 | 6.81 | 105 |
| 2002 | 7.23 | 102 |
| 2001 | 6.16 | 112 |
| 2000 | 5.99 | 111 |
| 1999 | 6.27 | 106 |
| 1998 | 6.12 | 112 |
| 1997 | 6.57 | 107 |
| 1996 | 7 | 107 |
| 1995 | 8.24 | 103 |
| 1994 | 8.19 | 98 |
| 1993 | 8.58 | 94 |
| 1992 | 9.09 | 90 |
| 1991 | 10.52 | 86 |
| 1990 | 10.56 | 86 |
| 1989 | 12.22 | 77 |
| 1988 | 13.82 | 72 |
| 1987 | 14.43 | 64 |
| 1986 | 12.82 | 70 |