| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 31.74 | 39 |
| 2015 | 29.82 | 56 |
| 2014 | 27.42 | 80 |
| 2013 | 25.97 | 95 |
| 2012 | 24.59 | 101 |
| 2011 | 23.78 | 112 |
| 2010 | 23.53 | 110 |
| 2009 | 23.33 | 103 |
| 2008 | 24.07 | 108 |
| 2007 | 27.1 | 94 |
| 2006 | 27.86 | 89 |
| 2005 | 26.64 | 96 |
| 2004 | 27.47 | 85 |
| 2003 | 26.51 | 92 |
| 2002 | 25.86 | 96 |
| 2001 | 23.68 | 115 |
| 2000 | 23.3 | 112 |
| 1999 | 19.29 | 133 |
| 1998 | 17.6 | 140 |
| 1997 | 17.3 | 140 |
| 1996 | 15.82 | 141 |
| 1995 | 14.96 | 143 |
| 1994 | 14.4 | 129 |
| 1993 | 13.02 | 128 |