| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 26.18 | 46 |
| 2014 | 18.48 | 81 |
| 2013 | 15.61 | 105 |
| 2012 | 17.2 | 98 |
| 2011 | 18.9 | 88 |
| 2010 | 21.48 | 72 |
| 2009 | 23.8 | 60 |
| 2008 | 18.82 | 90 |
| 2007 | 20.51 | 77 |
| 2006 | 18.79 | 86 |
| 2005 | 16.7 | 93 |
| 2004 | 18.95 | 79 |
| 2003 | 20.38 | 65 |
| 2002 | 19.63 | 66 |
| 2001 | 20.12 | 62 |
| 2000 | 17.88 | 66 |
| 1999 | 22.35 | 49 |
| 1998 | 28.19 | 35 |
| 1997 | 22.7 | 43 |
| 1996 | 20.84 | 51 |
| 1995 | 24.8 | 35 |
| 1994 | 23.8 | 40 |
| 1993 | 24.15 | 37 |
| 1992 | 30.64 | 26 |
| 1991 | 55.25 | 7 |
| 1990 | 25.17 | 29 |
| 1989 | 22.47 | 36 |
| 1988 | 25.91 | 33 |
| 1987 | 22.83 | 36 |
| 1986 | 27.45 | 28 |