| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 17.77 | 37 |
| 2015 | 19.33 | 39 |
| 2014 | 20.38 | 36 |
| 2013 | 20.74 | 41 |
| 2012 | 20.07 | 41 |
| 2011 | 22.82 | 35 |
| 2010 | 19.15 | 45 |
| 2009 | 18.91 | 45 |
| 2008 | 18.4 | 49 |
| 2007 | 20.28 | 46 |
| 2006 | 20.45 | 45 |
| 2005 | 20.89 | 46 |
| 2004 | 24.66 | 37 |
| 2003 | 23.68 | 41 |
| 2002 | 25.96 | 36 |
| 2001 | 28.33 | 28 |
| 2000 | 25.55 | 40 |
| 1999 | 29.46 | 30 |
| 1998 | 34 | 26 |
| 1997 | 31.97 | 32 |
| 1996 | 36.83 | 24 |
| 1995 | 42.26 | 17 |
| 1994 | 44.87 | 14 |
| 1993 | 51.37 | 9 |
| 1992 | 31.04 | 30 |
| 1991 | 24.97 | 45 |
| 1990 | 17.38 | 66 |