| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.51 | 26 |
| 2015 | 6.19 | 33 |
| 2014 | 6.99 | 28 |
| 2013 | 7.53 | 28 |
| 2012 | 6.22 | 51 |
| 2011 | 10.7 | 26 |
| 2010 | 8.13 | 27 |
| 2009 | 5.42 | 54 |
| 2008 | 8.9 | 89 |
| 2007 | 9.11 | 32 |
| 2006 | 6.77 | 61 |
| 2005 | 7.05 | 59 |
| 2004 | 7.59 | 43 |
| 2003 | 5.67 | 61 |
| 2002 | 3.33 | 78 |
| 2001 | 2.01 | 130 |
| 2000 | 2.21 | 114 |
| 1999 | 6.11 | 54 |
| 1998 | 8.4 | 52 |
| 1997 | 5.31 | 85 |
| 1996 | 2.38 | 129 |
| 1995 | 10.3 | 69 |
| 1994 | 5.31 | 101 |
| 1993 | 3.01 | 111 |
| 1992 | 3.63 | 103 |
| 1991 | 6.36 | 87 |
| 1990 | 6.13 | 86 |
| 1989 | 6.05 | 82 |
| 1988 | 7.41 | 65 |
| 1987 | 9.87 | 48 |