| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 7.5 | 34 |
| 2014 | 6.88 | 39 |
| 2013 | 3.57 | 83 |
| 2012 | 2.89 | 102 |
| 2011 | 3.64 | 92 |
| 2010 | 3.91 | 76 |
| 2009 | 5.46 | 56 |
| 2008 | 4.18 | 102 |
| 2007 | 7.66 | 68 |
| 2006 | 5.42 | 76 |
| 2005 | 1.01 | 156 |
| 2004 | 0.71 | 154 |
| 2003 | 0.96 | 140 |
| 2002 | 0.25 | 160 |
| 2001 | 1.35 | 118 |
| 2000 | 1.96 | 109 |
| 1999 | 3.55 | 70 |
| 1998 | 3.54 | 62 |
| 1997 | 4.94 | 37 |
| 1996 | 8.53 | 11 |
| 1995 | 5.39 | 24 |
| 1994 | 3.84 | 27 |
| 1993 | 2.25 | 35 |
| 1992 | 0.69 | 81 |
| 1991 | 0.67 | 78 |
| 1990 | 0.69 | 80 |
| 1989 | 0.56 | 73 |
| 1988 | 0.33 | 84 |