| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 21.12 | 4 |
| 2015 | 20.74 | 4 |
| 2014 | 20.31 | 4 |
| 2013 | 19.88 | 4 |
| 2012 | 19.46 | 4 |
| 2011 | 19.06 | 4 |
| 2010 | 18.69 | 4 |
| 2009 | 18.33 | 4 |
| 2008 | 18.02 | 5 |
| 2007 | 17.75 | 5 |
| 2006 | 17.5 | 5 |
| 2005 | 17.26 | 8 |
| 2004 | 17.09 | 9 |
| 2003 | 16.92 | 8 |
| 2002 | 16.73 | 9 |
| 2001 | 16.53 | 9 |
| 2000 | 16.31 | 9 |
| 1999 | 16.05 | 9 |
| 1998 | 15.79 | 9 |
| 1997 | 15.52 | 9 |
| 1996 | 15.27 | 10 |
| 1995 | 15.03 | 12 |
| 1994 | 14.75 | 11 |
| 1993 | 14.48 | 12 |
| 1992 | 14.22 | 12 |
| 1991 | 13.94 | 12 |
| 1990 | 13.66 | 12 |
| 1989 | 13.33 | 13 |
| 1988 | 13.01 | 15 |
| 1987 | 12.7 | 15 |
| 1986 | 12.41 | 15 |