| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 18.72 | 5 |
| 2015 | 19.01 | 5 |
| 2014 | 19.42 | 5 |
| 2013 | 19.97 | 5 |
| 2012 | 20.63 | 7 |
| 2011 | 21.33 | 15 |
| 2010 | 22 | 22 |
| 2009 | 22.82 | 27 |
| 2008 | 23.68 | 31 |
| 2007 | 24.52 | 31 |
| 2006 | 25.31 | 32 |
| 2005 | 26.04 | 32 |
| 2004 | 26.63 | 31 |
| 2003 | 27.03 | 30 |
| 2002 | 27.33 | 28 |
| 2001 | 27.79 | 28 |
| 2000 | 28.56 | 28 |
| 1999 | 29.18 | 30 |
| 1998 | 30.13 | 31 |
| 1997 | 31.23 | 32 |
| 1996 | 32.09 | 35 |
| 1995 | 32.44 | 34 |
| 1994 | 33.26 | 36 |
| 1993 | 33.79 | 37 |
| 1992 | 34.24 | 36 |
| 1991 | 35.1 | 38 |
| 1990 | 36.68 | 43 |
| 1989 | 38.13 | 44 |
| 1988 | 40.07 | 48 |
| 1987 | 42.29 | 52 |
| 1986 | 44.32 | 54 |