| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.88 | 7 |
| 2015 | 6.76 | 4 |
| 2014 | 6.23 | 11 |
| 2013 | 5.1 | 22 |
| 2012 | 4.13 | 42 |
| 2011 | 5.25 | 39 |
| 2010 | 8.76 | 11 |
| 2009 | 6.95 | 7 |
| 2008 | 2.38 | 97 |
| 2007 | 8.15 | 33 |
| 2006 | 7.58 | 31 |
| 2005 | 7.57 | 29 |
| 2004 | 6.19 | 47 |
| 2003 | 6.09 | 37 |
| 2002 | 2.06 | 83 |
| 2001 | 3.02 | 61 |
| 2000 | 2.02 | 127 |
| 1999 | 6.89 | 19 |
| 1998 | 4.24 | 47 |
| 1997 | 2.12 | 109 |
| 1996 | 5.53 | 38 |
| 1995 | 5.53 | 36 |
| 1994 | 4.6 | 41 |
| 1993 | 2.71 | 60 |
| 1992 | 3.39 | 48 |
| 1991 | -.98 | 108 |
| 1990 | 3.37 | 55 |
| 1989 | 3.74 | 46 |
| 1988 | 7.3 | 27 |
| 1987 | 1.72 | 77 |
| 1986 | 2.48 | 62 |