| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 19.16 | 43 |
| 2015 | 19.44 | 72 |
| 2014 | 18.51 | 80 |
| 2013 | 17.18 | 96 |
| 2012 | 16.3 | 102 |
| 2011 | 15.36 | 104 |
| 2010 | 14.49 | 114 |
| 2009 | 13.74 | 116 |
| 2008 | 14.34 | 115 |
| 2007 | 13.75 | 123 |
| 2006 | 13.41 | 121 |
| 2005 | 13.05 | 117 |
| 2004 | 12.63 | 113 |
| 2003 | 12.75 | 110 |
| 2002 | 13.84 | 100 |
| 2001 | 13.56 | 98 |
| 2000 | 13.25 | 94 |
| 1999 | 13.16 | 96 |
| 1998 | 10.92 | 107 |
| 1997 | 10.63 | 102 |
| 1996 | 10.29 | 104 |
| 1995 | 10.35 | 100 |
| 1994 | 10.37 | 99 |
| 1993 | 11.78 | 93 |
| 1992 | 11.79 | 81 |
| 1991 | 11.41 | 80 |
| 1990 | 10.98 | 80 |
| 1989 | 10.44 | 78 |
| 1988 | 9.71 | 79 |
| 1987 | 9.89 | 79 |
| 1986 | 10.11 | 75 |