| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.82 | 79 |
| 2015 | 6.96 | 91 |
| 2014 | 7.67 | 88 |
| 2013 | 8.68 | 88 |
| 2012 | 9.27 | 80 |
| 2011 | 10.12 | 76 |
| 2010 | 8.24 | 92 |
| 2009 | 8.98 | 88 |
| 2008 | 10.54 | 73 |
| 2007 | 9.88 | 80 |
| 2006 | 10.4 | 79 |
| 2005 | 10.09 | 84 |
| 2004 | 12.88 | 74 |
| 2003 | 11.14 | 82 |
| 2002 | 8.69 | 95 |
| 2001 | 6.52 | 109 |
| 2000 | 6.96 | 104 |
| 1999 | 6.78 | 103 |
| 1998 | 7.97 | 101 |
| 1997 | 7.71 | 100 |
| 1996 | 8.02 | 101 |
| 1995 | 8.62 | 101 |
| 1994 | 7.93 | 100 |
| 1993 | 7.37 | 100 |
| 1992 | 8.82 | 93 |
| 1991 | 8.5 | 93 |
| 1990 | 9.21 | 89 |
| 1989 | 10.9 | 79 |
| 1988 | 12.04 | 77 |
| 1987 | 13.71 | 67 |
| 1986 | 12.65 | 71 |