| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 2.11 | 19 |
| 2015 | 2.1 | 24 |
| 2014 | 2.1 | 27 |
| 2013 | 2.1 | 30 |
| 2012 | 2.13 | 29 |
| 2011 | 2.17 | 32 |
| 2010 | 2.21 | 30 |
| 2009 | 2.26 | 25 |
| 2008 | 2.29 | 25 |
| 2007 | 2.3 | 28 |
| 2006 | 2.29 | 30 |
| 2005 | 2.25 | 30 |
| 2004 | 2.21 | 34 |
| 2003 | 2.23 | 35 |
| 2002 | 2.34 | 31 |
| 2001 | 2.5 | 27 |
| 2000 | 2.73 | 20 |
| 1999 | 2.93 | 17 |
| 1998 | 2.9 | 16 |
| 1997 | 2.53 | 27 |
| 1996 | 1.88 | 51 |
| 1995 | 1.06 | 86 |
| 1994 | 0.33 | 117 |
| 1993 | -.09 | 147 |
| 1992 | -.07 | 154 |
| 1991 | 0.29 | 130 |
| 1990 | 0.86 | 100 |
| 1989 | 1.36 | 89 |
| 1988 | 1.6 | 71 |
| 1987 | 1.47 | 82 |
| 1986 | 1.03 | 99 |