| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 3.65 | 33 |
| 2015 | 3.6 | 33 |
| 2014 | 3.5 | 32 |
| 2013 | 3.1 | 25 |
| 2012 | 3.2 | 27 |
| 2011 | 3.4 | 29 |
| 2010 | 3.7 | 29 |
| 2009 | 3.6 | 29 |
| 2008 | 3.2 | 31 |
| 2007 | 3.2 | 31 |
| 2006 | 3.5 | 31 |
| 2005 | 3.7 | 29 |
| 2004 | 3.7 | 30 |
| 2003 | 3.6 | 27 |
| 2002 | 3.3 | 27 |
| 2001 | 4 | 38 |
| 2000 | 4.4 | 41 |
| 1999 | 6.34 | 68 |
| 1998 | 6.96 | 79 |
| 1997 | 2.61 | 22 |
| 1996 | 2.05 | 17 |
| 1995 | 2.06 | 15 |
| 1994 | 2.48 | 18 |
| 1993 | 2.88 | 25 |
| 1992 | 2.51 | 20 |
| 1991 | 2.41 | 22 |