| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 2.72 | 22 |
| 2015 | 1.8 | 12 |
| 2014 | 1.7 | 12 |
| 2013 | 1.8 | 13 |
| 2012 | 2 | 15 |
| 2011 | 2.6 | 14 |
| 2010 | 2.8 | 18 |
| 2009 | 3.5 | 27 |
| 2008 | 3 | 27 |
| 2007 | 3 | 25 |
| 2006 | 3.7 | 36 |
| 2005 | 4.2 | 35 |
| 2004 | 4.9 | 50 |
| 2003 | 6.1 | 64 |
| 2002 | 6.4 | 69 |
| 2001 | 6.5 | 69 |
| 2000 | 6.7 | 75 |
| 1999 | 6.3 | 66 |
| 1998 | 4.5 | 42 |
| 1997 | 3.1 | 28 |
| 1996 | 4.2 | 38 |
| 1995 | 3.6 | 34 |
| 1994 | 2.4 | 16 |
| 1993 | 2 | 15 |
| 1992 | 2.3 | 15 |
| 1991 | 3 | 33 |