| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 31.36 | 50 |
| 2014 | 30.22 | 59 |
| 2013 | 31.66 | 53 |
| 2012 | 30.29 | 63 |
| 2011 | 29.5 | 68 |
| 2010 | 28.4 | 77 |
| 2009 | 28.67 | 67 |
| 2008 | 28.65 | 81 |
| 2007 | 28.31 | 84 |
| 2006 | 29.33 | 79 |
| 2005 | 29.3 | 73 |
| 2004 | 30.22 | 68 |
| 2003 | 31.84 | 51 |
| 2002 | 32.3 | 54 |
| 2001 | 32.93 | 49 |
| 2000 | 33.45 | 50 |
| 1999 | 30.3 | 60 |
| 1998 | 31.93 | 49 |
| 1997 | 30.81 | 60 |
| 1996 | 33.11 | 44 |
| 1995 | 35.47 | 32 |