| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.08 | 27 |
| 2015 | 6.22 | 39 |
| 2014 | 7.39 | 32 |
| 2013 | 7.99 | 37 |
| 2012 | 8.36 | 25 |
| 2011 | 10.69 | 27 |
| 2010 | 12.68 | 18 |
| 2009 | 10.29 | 17 |
| 2008 | 9.84 | 23 |
| 2007 | 15.05 | 12 |
| 2006 | 13.45 | 27 |
| 2005 | 12.13 | 18 |
| 2004 | 11.14 | 32 |
| 2003 | 12.67 | 23 |
| 2002 | 9.9 | 22 |
| 2001 | 8.48 | 27 |
| 2000 | 9.48 | 37 |
| 1999 | 8.19 | 31 |
| 1998 | 8.91 | 26 |
| 1997 | 10.47 | 26 |
| 1996 | 12.09 | 16 |
| 1995 | 13.84 | 13 |
| 1994 | 18.13 | 5 |
| 1993 | 19.76 | 5 |
| 1992 | 21.02 | 5 |
| 1991 | 13.77 | 12 |
| 1990 | 3.2 | 53 |
| 1989 | 3.75 | 63 |
| 1988 | 14.31 | 13 |
| 1987 | 13.59 | 12 |
| 1986 | 10.22 | 23 |