| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 4.31 | 44 |
| 2015 | 4.62 | 49 |
| 2014 | 4.98 | 54 |
| 2013 | 5.23 | 60 |
| 2012 | 5.38 | 61 |
| 2011 | 5.82 | 66 |
| 2010 | 6.97 | 81 |
| 2009 | 7.74 | 95 |
| 2008 | 7.53 | 110 |
| 2007 | 8.66 | 123 |
| 2006 | 10.25 | 133 |
| 2005 | 11.17 | 137 |
| 2004 | 10.73 | 131 |
| 2003 | 9.78 | 116 |
| 2002 | 8.48 | 97 |
| 2001 | 7.77 | 94 |
| 2000 | 7.92 | 96 |
| 1999 | 8.85 | 104 |
| 1998 | 9.79 | 115 |
| 1997 | 9.86 | 114 |
| 1996 | 8.82 | 101 |
| 1995 | 8.16 | 96 |
| 1994 | 8.73 | 105 |
| 1993 | 7.68 | 91 |
| 1992 | 6.32 | 72 |
| 1991 | 5.32 | 58 |