| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 18.04 | 24 |
| 2015 | 17.41 | 25 |
| 2014 | 16.66 | 27 |
| 2013 | 15.86 | 27 |
| 2012 | 15.04 | 30 |
| 2011 | 14.23 | 32 |
| 2010 | 13.47 | 36 |
| 2009 | 12.82 | 41 |
| 2008 | 12.2 | 45 |
| 2007 | 11.61 | 49 |
| 2006 | 11.05 | 51 |
| 2005 | 10.55 | 53 |
| 2004 | 10.08 | 53 |
| 2003 | 9.69 | 56 |
| 2002 | 9.33 | 56 |
| 2001 | 9 | 56 |
| 2000 | 8.66 | 56 |
| 1999 | 8.29 | 56 |
| 1998 | 7.97 | 56 |
| 1997 | 7.7 | 57 |
| 1996 | 7.52 | 60 |
| 1995 | 7.4 | 60 |
| 1994 | 7.18 | 60 |
| 1993 | 6.96 | 61 |
| 1992 | 6.72 | 62 |
| 1991 | 6.48 | 62 |
| 1990 | 6.23 | 63 |
| 1989 | 5.99 | 64 |
| 1988 | 5.77 | 64 |
| 1987 | 5.58 | 67 |
| 1986 | 5.43 | 67 |