| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 31.7 | 19 |
| 2015 | 29.63 | 37 |
| 2014 | 28.89 | 42 |
| 2013 | 28.45 | 51 |
| 2012 | 27.36 | 53 |
| 2011 | 26.49 | 55 |
| 2010 | 24.7 | 59 |
| 2009 | 21.37 | 76 |
| 2008 | 17.03 | 97 |
| 2007 | 18.67 | 90 |
| 2006 | 19.98 | 76 |
| 2005 | 20.57 | 74 |
| 2004 | 23.73 | 59 |
| 2003 | 21.73 | 59 |
| 2002 | 20.88 | 62 |
| 2001 | 23.04 | 51 |
| 2000 | 18.08 | 65 |
| 1999 | 18.1 | 65 |
| 1998 | 16.92 | 69 |
| 1997 | 17.27 | 65 |
| 1996 | 13.97 | 80 |
| 1995 | 7.07 | 128 |
| 1994 | 4.81 | 128 |
| 1993 | 5.5 | 124 |