| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.33 | 21 |
| 2015 | 4.59 | 47 |
| 2014 | 6.07 | 38 |
| 2013 | 5.75 | 47 |
| 2012 | 5.65 | 62 |
| 2011 | 5 | 89 |
| 2010 | 4.26 | 75 |
| 2009 | 7.13 | 38 |
| 2008 | 11.54 | 57 |
| 2007 | 7.1 | 61 |
| 2006 | 4.64 | 86 |
| 2005 | 3.4 | 103 |
| 2004 | 1.39 | 138 |
| 2003 | 5.86 | 58 |
| 2002 | 9.16 | 38 |
| 2001 | 5.7 | 59 |
| 2000 | 5.34 | 58 |
| 1999 | 5.18 | 63 |
| 1998 | 6.88 | 66 |
| 1997 | 8.6 | 52 |
| 1996 | 7.35 | 78 |
| 1995 | 8.68 | 87 |
| 1994 | 8.94 | 82 |
| 1993 | 9.72 | 70 |
| 1992 | 13.87 | 48 |
| 1991 | 15.33 | 50 |
| 1990 | 14.32 | 47 |
| 1989 | 14.73 | 38 |
| 1988 | 12.78 | 44 |
| 1987 | 16.16 | 33 |
| 1986 | 18.65 | 31 |