| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 13.72 | 46 |
| 2015 | 14.19 | 56 |
| 2014 | 11.65 | 64 |
| 2013 | 10.03 | 74 |
| 2012 | 9.05 | 83 |
| 2011 | 9.49 | 82 |
| 2010 | 8.42 | 89 |
| 2009 | 8.26 | 92 |
| 2008 | 7.9 | 91 |
| 2007 | 7.46 | 95 |
| 2006 | 8.68 | 91 |
| 2005 | 10.4 | 81 |
| 2004 | 11.93 | 77 |
| 2003 | 12.1 | 78 |
| 2002 | 14.62 | 68 |
| 2001 | 16.37 | 59 |
| 2000 | 17.08 | 60 |
| 1999 | 14.28 | 73 |
| 1998 | 14.24 | 74 |
| 1997 | 14.41 | 75 |
| 1996 | 13.83 | 78 |
| 1995 | 15.4 | 72 |
| 1994 | 16.24 | 69 |
| 1993 | 21.67 | 50 |
| 1992 | 20.36 | 54 |
| 1991 | 22.78 | 49 |
| 1990 | 25.57 | 45 |
| 1989 | 22.93 | 47 |
| 1988 | 20.94 | 50 |
| 1987 | 21.67 | 49 |