| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 6.01 | 34 |
| 2014 | 5.21 | 48 |
| 2013 | 4.96 | 62 |
| 2012 | 4.54 | 75 |
| 2011 | 4.44 | 103 |
| 2010 | 6.01 | 53 |
| 2009 | 6.92 | 43 |
| 2008 | 10.76 | 62 |
| 2007 | 0.91 | 168 |
| 2006 | 2.37 | 135 |
| 2005 | 1.78 | 148 |
| 2004 | 2.16 | 123 |
| 2003 | 14.71 | 21 |
| 2002 | 11.8 | 29 |
| 2001 | 9.3 | 29 |
| 2000 | 15.6 | 20 |
| 1999 | 14.93 | 25 |
| 1998 | 13.57 | 30 |
| 1997 | 3.96 | 98 |
| 1996 | 11.62 | 53 |
| 1995 | 17.28 | 51 |
| 1994 | 2.85 | 120 |
| 1993 | 4.97 | 90 |
| 1992 | 4.31 | 91 |
| 1991 | 6.97 | 83 |
| 1990 | 6.95 | 80 |
| 1989 | 4.48 | 95 |
| 1988 | 5.45 | 78 |
| 1987 | 3.34 | 87 |
| 1986 | 5.45 | 69 |