| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 0.26 | 2 |
| 2015 | 0.18 | 2 |
| 2014 | 0.1 | 1 |
| 2013 | 0.3 | 2 |
| 2012 | 0.2 | 1 |
| 2011 | 0.2 | 1 |
| 2010 | 0.35 | 1 |
| 2009 | 0.19 | 1 |
| 2008 | 0.44 | 2 |
| 2007 | 0.87 | 4 |
| 2006 | 1.46 | 10 |
| 2005 | 1.79 | 9 |
| 2004 | 2.12 | 12 |
| 2003 | 2.03 | 11 |
| 2002 | 1.92 | 12 |
| 2001 | 1.8 | 11 |
| 2000 | 2.5 | 20 |
| 1999 | 1.6 | 10 |
| 1998 | 0.75 | 4 |
| 1997 | 0.61 | 1 |
| 1996 | 0.84 | 6 |
| 1995 | 1.28 | 9 |
| 1994 | 1.78 | 12 |
| 1993 | 0.59 | 2 |
| 1992 | 0.23 | 1 |
| 1991 | 0.48 | 2 |