| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2014 | 6.8 | 97 |
| 2013 | 9.37 | 81 |
| 2012 | 7.91 | 90 |
| 2011 | 8.9 | 88 |
| 2010 | 9.38 | 84 |
| 2009 | 8.5 | 91 |
| 2008 | 7.82 | 92 |
| 2007 | 8.75 | 91 |
| 2006 | 6.69 | 101 |
| 2005 | 6.06 | 104 |
| 2004 | 6.85 | 101 |
| 2003 | 7.15 | 102 |
| 2002 | 7.47 | 99 |
| 2001 | 9.75 | 88 |
| 2000 | 9.56 | 88 |
| 1999 | 7.88 | 97 |
| 1998 | 7.54 | 102 |
| 1997 | 7.84 | 99 |
| 1996 | 8.29 | 99 |
| 1995 | 8.18 | 104 |
| 1994 | 8.34 | 96 |
| 1993 | 9.36 | 89 |
| 1992 | 8.87 | 92 |
| 1991 | 9.01 | 90 |
| 1990 | 8.17 | 95 |
| 1989 | 8.56 | 87 |
| 1988 | 8.25 | 85 |
| 1987 | 8.05 | 85 |
| 1986 | 7.61 | 81 |