| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 12.95 | 52 |
| 2015 | 12.67 | 60 |
| 2014 | 11.07 | 68 |
| 2013 | 10.64 | 71 |
| 2012 | 9.4 | 78 |
| 2011 | 8.62 | 90 |
| 2010 | 9.03 | 87 |
| 2009 | 10.07 | 77 |
| 2008 | 7 | 97 |
| 2007 | 8.03 | 93 |
| 2006 | 8.01 | 95 |
| 2005 | 8.23 | 95 |
| 2004 | 10.18 | 86 |
| 2003 | 10.63 | 85 |
| 2002 | 10.07 | 86 |
| 2001 | 10.5 | 85 |
| 2000 | 8.98 | 90 |
| 1999 | 11.94 | 81 |
| 1998 | 12.53 | 84 |
| 1997 | 9.48 | 91 |
| 1996 | 11.77 | 86 |
| 1995 | 10.5 | 91 |
| 1994 | 10.06 | 87 |
| 1993 | 12.1 | 77 |
| 1992 | 12.13 | 81 |
| 1991 | 10.17 | 89 |
| 1990 | 11.36 | 85 |
| 1989 | 13.04 | 74 |
| 1988 | 12.17 | 76 |
| 1987 | 12.87 | 72 |
| 1986 | 10.18 | 76 |