| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 30.97 | 51 |
| 2014 | 31.8 | 51 |
| 2013 | 32.46 | 49 |
| 2012 | 32.39 | 51 |
| 2011 | 30.08 | 63 |
| 2010 | 30.18 | 58 |
| 2009 | 31.61 | 54 |
| 2008 | 37.38 | 40 |
| 2007 | 34.77 | 49 |
| 2006 | 34.64 | 48 |
| 2005 | 29.18 | 75 |
| 2004 | 29.42 | 73 |
| 2003 | 28.35 | 79 |
| 2002 | 32.32 | 53 |
| 2001 | 30.92 | 62 |
| 2000 | 27.96 | 82 |
| 1999 | 24.17 | 109 |
| 1998 | 25.4 | 97 |
| 1997 | 24.4 | 105 |
| 1996 | 23.67 | 111 |
| 1995 | 24.44 | 107 |
| 1994 | 26.93 | 79 |
| 1993 | 25.28 | 85 |
| 1992 | 27.66 | 75 |
| 1991 | 28.1 | 74 |
| 1990 | 31.52 | 58 |
| 1989 | 36.53 | 30 |
| 1988 | 35.71 | 31 |
| 1987 | 32.36 | 47 |
| 1986 | 37.95 | 20 |