| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 34.69 | 30 |
| 2014 | 28.94 | 41 |
| 2013 | 28.16 | 53 |
| 2012 | 25.3 | 60 |
| 2011 | 22.75 | 70 |
| 2010 | 23.49 | 64 |
| 2009 | 21.43 | 74 |
| 2008 | 19.67 | 84 |
| 2007 | 20.07 | 79 |
| 2006 | 21.26 | 72 |
| 2005 | 21.43 | 69 |
| 2004 | 20.61 | 64 |
| 2003 | 22.13 | 56 |
| 2002 | 23.06 | 53 |
| 2001 | 21.47 | 59 |
| 2000 | 21.72 | 53 |
| 1999 | 15.75 | 76 |
| 1998 | 19.66 | 61 |
| 1997 | 12.75 | 90 |