| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 11.09 | 7 |
| 2015 | 9.67 | 15 |
| 2014 | 8.16 | 24 |
| 2013 | 9.64 | 23 |
| 2012 | 9.44 | 18 |
| 2011 | 9.02 | 38 |
| 2010 | 7.03 | 64 |
| 2009 | 6.91 | 25 |
| 2008 | 7.03 | 43 |
| 2007 | 9.03 | 42 |
| 2006 | 9.8 | 43 |
| 2005 | 7.93 | 43 |
| 2004 | 7.05 | 62 |
| 2003 | 6.58 | 63 |
| 2002 | 5.8 | 53 |
| 2001 | 7.46 | 32 |
| 2000 | 6.26 | 60 |
| 1999 | 5.24 | 60 |
| 1998 | 8.73 | 28 |
| 1997 | 5.23 | 69 |
| 1996 | 6.74 | 41 |
| 1995 | 10.13 | 23 |
| 1994 | 8.13 | 33 |
| 1993 | 8.09 | 22 |
| 1992 | 6.99 | 37 |
| 1991 | 4.71 | 38 |
| 1990 | 7.3 | 32 |
| 1989 | 3.78 | 62 |
| 1988 | 3.12 | 66 |
| 1987 | 8.63 | 27 |
| 1986 | 6.91 | 34 |