| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 4.95 | 52 |
| 2015 | 4.42 | 46 |
| 2014 | 4.08 | 41 |
| 2013 | 4 | 40 |
| 2012 | 3.6 | 34 |
| 2011 | 3.9 | 36 |
| 2010 | 4 | 34 |
| 2009 | 4.4 | 40 |
| 2008 | 6.64 | 90 |
| 2007 | 6.47 | 84 |
| 2006 | 7.24 | 95 |
| 2005 | 8.31 | 106 |
| 2004 | 9.03 | 110 |
| 2003 | 8.31 | 97 |
| 2002 | 7.7 | 89 |
| 2001 | 7.88 | 97 |
| 2000 | 7.34 | 87 |
| 1999 | 7.99 | 95 |
| 1998 | 7.75 | 93 |
| 1997 | 7.69 | 89 |
| 1996 | 7.07 | 83 |
| 1995 | 6.44 | 68 |
| 1994 | 7.21 | 84 |
| 1993 | 7.11 | 88 |
| 1992 | 9.4 | 114 |
| 1991 | 4.74 | 53 |