| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 3.14 | 26 |
| 2015 | 3.4 | 30 |
| 2014 | 3.6 | 35 |
| 2013 | 4 | 39 |
| 2012 | 4.3 | 46 |
| 2011 | 4.52 | 49 |
| 2010 | 5.1 | 50 |
| 2009 | 5.1 | 46 |
| 2008 | 4 | 45 |
| 2007 | 3.9 | 41 |
| 2006 | 4.1 | 43 |
| 2005 | 4.4 | 41 |
| 2004 | 4.7 | 49 |
| 2003 | 5.3 | 51 |
| 2002 | 5.4 | 54 |
| 2001 | 5 | 52 |
| 2000 | 4.7 | 49 |
| 1999 | 4.7 | 43 |
| 1998 | 4.1 | 39 |
| 1997 | 3.4 | 32 |
| 1996 | 3.4 | 29 |
| 1995 | 3.2 | 27 |
| 1994 | 2.9 | 26 |
| 1993 | 2.5 | 20 |
| 1992 | 2.2 | 13 |
| 1991 | 2.1 | 17 |