| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 4.78 | 45 |
| 2014 | 2.92 | 82 |
| 2013 | 3.25 | 81 |
| 2012 | 8.89 | 33 |
| 2011 | 4.52 | 99 |
| 2010 | 3.91 | 82 |
| 2009 | 5.73 | 51 |
| 2008 | 4.86 | 137 |
| 2007 | 3.67 | 114 |
| 2006 | 2.31 | 140 |
| 2005 | 1.38 | 157 |
| 2004 | 3.96 | 80 |
| 2003 | 4.27 | 73 |
| 2002 | 1.42 | 136 |
| 2001 | 4.23 | 82 |
| 2000 | 0.34 | 145 |
| 1999 | 2.65 | 91 |
| 1998 | 4.95 | 85 |
| 1997 | 5.73 | 80 |
| 1996 | 18.68 | 43 |
| 1995 | 29.78 | 31 |
| 1994 | 29.05 | 44 |
| 1993 | 20.54 | 43 |
| 1992 | 31.67 | 24 |
| 1991 | 25.89 | 33 |
| 1990 | 16.65 | 43 |
| 1989 | 9.3 | 57 |
| 1988 | 5.91 | 76 |
| 1987 | 7.44 | 60 |
| 1986 | 12.37 | 43 |