| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.6 | 13 |
| 2015 | 6.8 | 25 |
| 2014 | 6.9 | 31 |
| 2013 | 6.8 | 36 |
| 2012 | 7 | 29 |
| 2011 | 6.6 | 47 |
| 2010 | 6.8 | 36 |
| 2009 | 5.7 | 42 |
| 2008 | 4.5 | 77 |
| 2007 | 6.1 | 43 |
| 2006 | 5.31 | 51 |
| 2005 | 6.2 | 43 |
| 2004 | 10.1 | 31 |
| 2003 | 6.8 | 39 |
| 2002 | 6 | 36 |
| 2001 | 4.1 | 60 |
| 2000 | 3.2 | 72 |
| 1999 | 5.5 | 51 |
| 1998 | 4.1 | 52 |
| 1997 | 5.8 | 33 |
| 1996 | -5.7 | 145 |
| 1995 | 2 | 78 |
| 1994 | -3.4 | 103 |
| 1993 | 1.5 | 68 |
| 1992 | -6.47 | 110 |
| 1991 | 2.22 | 61 |
| 1990 | 5.82 | 34 |
| 1989 | -3.46 | 94 |
| 1988 | 9.82 | 22 |