| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 0.23 | 1 |
| 2015 | 0.16 | 1 |
| 2014 | 0.21 | 2 |
| 2013 | 0.29 | 1 |
| 2012 | 0.46 | 2 |
| 2011 | 0.58 | 2 |
| 2010 | 0.45 | 2 |
| 2009 | 0.35 | 2 |
| 2008 | 0.35 | 1 |
| 2007 | 0.57 | 1 |
| 2006 | 1.37 | 8 |
| 2005 | 1.56 | 7 |
| 2004 | 2.07 | 9 |
| 2003 | 3.83 | 31 |
| 2002 | 4.7 | 45 |
| 2001 | 5.39 | 56 |
| 2000 | 1.42 | 8 |
| 1999 | 0.29 | 1 |
| 1998 | 0.47 | 1 |
| 1997 | 2.84 | 25 |
| 1996 | 0.3 | 1 |
| 1995 | 0.32 | 1 |
| 1994 | 0.37 | 1 |
| 1993 | 0.41 | 1 |
| 1992 | 0.47 | 2 |
| 1991 | 0.75 | 4 |