| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.55 | 4 |
| 2015 | 6.32 | 4 |
| 2014 | 5.54 | 6 |
| 2013 | 4.84 | 8 |
| 2012 | 4.46 | 9 |
| 2011 | 4.33 | 11 |
| 2010 | 3.52 | 18 |
| 2009 | 3.85 | 20 |
| 2008 | 3.02 | 28 |
| 2007 | 2.92 | 28 |
| 2006 | 2.64 | 36 |
| 2005 | 2.83 | 31 |
| 2004 | 3.28 | 24 |
| 2003 | 3.25 | 30 |
| 2002 | 3.7 | 23 |
| 2001 | 3.82 | 25 |
| 2000 | 3.43 | 31 |
| 1999 | 3.76 | 27 |
| 1998 | 3.97 | 24 |
| 1997 | 3.64 | 31 |
| 1996 | 3.09 | 34 |
| 1995 | 2.96 | 37 |
| 1994 | 3.14 | 34 |
| 1993 | 2.56 | 55 |
| 1992 | 2.19 | 67 |
| 1991 | 1.24 | 101 |
| 1990 | 1.46 | 93 |
| 1989 | 1.54 | 87 |
| 1988 | 1.74 | 86 |
| 1987 | 1.79 | 82 |
| 1986 | 1.77 | 77 |