| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 19.21 | 42 |
| 2015 | 17.85 | 80 |
| 2014 | 18.51 | 79 |
| 2013 | 20.05 | 82 |
| 2012 | 18.97 | 85 |
| 2011 | 18.85 | 89 |
| 2010 | 17.61 | 91 |
| 2009 | 17.27 | 93 |
| 2008 | 18.33 | 92 |
| 2007 | 16.36 | 100 |
| 2006 | 15.67 | 102 |
| 2005 | 15.49 | 100 |
| 2004 | 14.87 | 99 |
| 2003 | 14.41 | 99 |
| 2002 | 13.25 | 106 |
| 2001 | 13.06 | 105 |
| 2000 | 12.81 | 99 |
| 1999 | 12.84 | 98 |
| 1998 | 11.23 | 104 |
| 1997 | 10.41 | 105 |
| 1996 | 9.93 | 108 |
| 1995 | 8.8 | 118 |
| 1994 | 7.74 | 116 |
| 1993 | 14.62 | 70 |
| 1992 | 13.08 | 76 |
| 1991 | 13.86 | 66 |
| 1990 | 17.05 | 53 |
| 1989 | 13.94 | 63 |
| 1988 | 6.67 | 102 |
| 1987 | 4.93 | 109 |
| 1986 | 6.54 | 100 |