| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.92 | 11 |
| 2015 | 6.07 | 24 |
| 2014 | 6.15 | 29 |
| 2013 | 7.06 | 25 |
| 2012 | 6.68 | 31 |
| 2011 | 3.66 | 106 |
| 2010 | 7.63 | 38 |
| 2009 | 1.15 | 89 |
| 2008 | 4.15 | 93 |
| 2007 | 6.62 | 78 |
| 2006 | 5.24 | 107 |
| 2005 | 4.78 | 98 |
| 2004 | 6.7 | 63 |
| 2003 | 4.97 | 77 |
| 2002 | 3.65 | 92 |
| 2001 | 2.89 | 104 |
| 2000 | 4.41 | 93 |
| 1999 | 3.08 | 106 |
| 1998 | -.58 | 171 |
| 1997 | 5.19 | 76 |
| 1996 | 5.85 | 60 |
| 1995 | 4.68 | 76 |
| 1994 | 4.39 | 72 |
| 1993 | 2.12 | 96 |
| 1992 | 0.34 | 122 |
| 1991 | -.58 | 130 |
| 1990 | 3.04 | 90 |
| 1989 | 6.21 | 38 |
| 1988 | 6.75 | 48 |
| 1987 | 4.31 | 63 |
| 1986 | 3.42 | 82 |