| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 10.82 | 114 |
| 2014 | 12.9 | 116 |
| 2013 | 12.01 | 134 |
| 2012 | 13.68 | 126 |
| 2011 | 14.07 | 122 |
| 2010 | 17.6 | 92 |
| 2009 | 18.76 | 87 |
| 2008 | 26.12 | 58 |
| 2007 | 26.28 | 55 |
| 2006 | 25.77 | 58 |
| 2005 | 28.04 | 48 |
| 2004 | 28.18 | 43 |
| 2003 | 21.16 | 60 |
| 2002 | 18.15 | 75 |
| 2001 | 16.47 | 82 |
| 2000 | 17.34 | 70 |
| 1999 | 17.58 | 67 |
| 1998 | 17.25 | 68 |
| 1997 | 20.59 | 56 |
| 1996 | 21.23 | 48 |
| 1995 | 22.38 | 41 |
| 1994 | 26.43 | 33 |
| 1993 | 28.47 | 31 |
| 1992 | 30.06 | 28 |
| 1991 | 27.45 | 31 |
| 1990 | 22.63 | 32 |
| 1989 | 18.88 | 44 |
| 1988 | 21.37 | 38 |
| 1987 | 15.72 | 50 |
| 1986 | 17.75 | 48 |