| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.88 | 13 |
| 2015 | 7.04 | 12 |
| 2014 | 7.07 | 18 |
| 2013 | 7.43 | 19 |
| 2012 | 7.31 | 26 |
| 2011 | 7.07 | 38 |
| 2010 | 5.96 | 68 |
| 2009 | 0.09 | 102 |
| 2008 | 6.69 | 47 |
| 2007 | 10.21 | 24 |
| 2006 | 10.77 | 17 |
| 2005 | 13.25 | 8 |
| 2004 | 10.34 | 19 |
| 2003 | 8.51 | 29 |
| 2002 | 6.58 | 26 |
| 2001 | 8.15 | 18 |
| 2000 | 8.77 | 21 |
| 1999 | 11.91 | 7 |
| 1998 | 5.01 | 56 |
| 1997 | 5.62 | 64 |
| 1996 | 5.41 | 70 |
| 1995 | 6.44 | 46 |
| 1994 | 9.1 | 15 |