| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2014 | 28.2 | 17 |
| 2013 | 27.98 | 20 |
| 2012 | 27.96 | 22 |
| 2011 | 25.63 | 28 |
| 2010 | 23.09 | 34 |
| 2009 | 22.6 | 37 |
| 2008 | 23.38 | 38 |
| 2007 | 23.69 | 34 |
| 2006 | 23.79 | 37 |
| 2005 | 25.31 | 34 |
| 2004 | 26.65 | 32 |
| 2003 | 25.74 | 35 |
| 2002 | 27.47 | 29 |
| 2001 | 26.93 | 31 |
| 2000 | 26.18 | 35 |
| 1999 | 28.54 | 31 |
| 1998 | 29.25 | 37 |
| 1997 | 16.75 | 69 |
| 1996 | 17.6 | 66 |
| 1995 | 16.44 | 69 |
| 1994 | 16.28 | 68 |
| 1993 | 18.07 | 61 |
| 1992 | 16.2 | 66 |
| 1991 | 16.56 | 69 |
| 1990 | 20.88 | 55 |
| 1989 | 20.29 | 54 |
| 1988 | 20.02 | 52 |
| 1987 | 20.37 | 52 |
| 1986 | 23.94 | 41 |