| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.56 | 75 |
| 2015 | 6.04 | 96 |
| 2014 | 8 | 86 |
| 2013 | 7.21 | 95 |
| 2012 | 6.89 | 96 |
| 2011 | 8.33 | 91 |
| 2010 | 8.5 | 88 |
| 2009 | 6.29 | 103 |
| 2008 | 8.73 | 87 |
| 2007 | 8.83 | 90 |
| 2006 | 8.17 | 93 |
| 2005 | 9.33 | 90 |
| 2004 | 9.84 | 88 |
| 2003 | 11.04 | 83 |
| 2002 | 10.82 | 84 |
| 2001 | 4.89 | 121 |
| 2000 | 5.05 | 119 |
| 1999 | 4.82 | 115 |
| 1998 | 5.7 | 114 |
| 1997 | 5.67 | 113 |
| 1996 | 6.08 | 112 |
| 1995 | 5.79 | 117 |
| 1994 | 5.51 | 108 |
| 1993 | 5.49 | 107 |
| 1992 | 5.99 | 103 |
| 1991 | 6.72 | 100 |
| 1990 | 8.12 | 96 |
| 1989 | 9.62 | 82 |
| 1988 | 8.98 | 84 |
| 1987 | 8.09 | 84 |
| 1986 | 7.8 | 80 |