| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 2.79 | 7 |
| 2015 | 2.73 | 10 |
| 2014 | 2.67 | 12 |
| 2013 | 2.65 | 13 |
| 2012 | 2.7 | 13 |
| 2011 | 2.8 | 13 |
| 2010 | 2.93 | 12 |
| 2009 | 3.03 | 13 |
| 2008 | 3.09 | 12 |
| 2007 | 3.11 | 13 |
| 2006 | 3.07 | 12 |
| 2005 | 3.04 | 13 |
| 2004 | 2.99 | 15 |
| 2003 | 2.84 | 17 |
| 2002 | 2.55 | 24 |
| 2001 | 2.16 | 34 |
| 2000 | 1.69 | 50 |
| 1999 | 1.26 | 75 |
| 1998 | 0.98 | 82 |
| 1997 | 0.95 | 86 |
| 1996 | 1.1 | 85 |
| 1995 | 1.32 | 73 |
| 1994 | 1.52 | 69 |
| 1993 | 1.73 | 60 |
| 1992 | 1.93 | 54 |
| 1991 | 2.11 | 50 |
| 1990 | 2.29 | 36 |
| 1989 | 2.54 | 32 |
| 1988 | 2.71 | 26 |
| 1987 | 2.76 | 29 |
| 1986 | 2.72 | 31 |