| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 6.95 | 42 |
| 2014 | 6.7 | 41 |
| 2013 | 3.52 | 86 |
| 2012 | 4.76 | 66 |
| 2011 | 2.83 | 102 |
| 2010 | 4.93 | 62 |
| 2009 | 8.67 | 33 |
| 2008 | 12.34 | 26 |
| 2007 | 9.61 | 46 |
| 2006 | 6.64 | 64 |
| 2005 | 5.19 | 66 |
| 2004 | 6.98 | 39 |
| 2003 | 8.99 | 21 |
| 2002 | 5.96 | 33 |
| 2001 | 4.99 | 44 |
| 2000 | 5.24 | 48 |
| 1999 | 6.71 | 36 |
| 1998 | 2.52 | 89 |
| 1997 | 8.59 | 15 |
| 1996 | 7.53 | 15 |
| 1995 | 24.14 | 3 |
| 1994 | 10.49 | 9 |
| 1993 | 6.59 | 13 |
| 1992 | 10.64 | 5 |
| 1991 | 8.44 | 8 |
| 1990 | 7.75 | 8 |
| 1989 | 11.21 | 3 |
| 1988 | 8.3 | 3 |
| 1987 | 10.7 | 4 |
| 1986 | 4.63 | 9 |