| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 2.1 | 78 |
| 2015 | 2.34 | 88 |
| 2014 | 3.38 | 75 |
| 2013 | 3.2 | 85 |
| 2012 | 3.25 | 71 |
| 2011 | 3.47 | 96 |
| 2010 | 2.7 | 73 |
| 2009 | 5.1 | 49 |
| 2008 | 7.5 | 43 |
| 2007 | 2.36 | 97 |
| 2006 | 2.35 | 96 |
| 2005 | 7.72 | 29 |
| 2004 | 5.91 | 54 |
| 2003 | 3.22 | 71 |
| 2002 | 5.04 | 45 |
| 2001 | 4.93 | 54 |
| 2000 | 4.46 | 58 |
| 1999 | 4.06 | 69 |
| 1998 | 1.91 | 82 |
| 1997 | 2.45 | 75 |
| 1996 | 3.87 | 69 |
| 1995 | 5.84 | 39 |
| 1994 | 2.11 | 63 |
| 1993 | 3.11 | 50 |
| 1992 | 1.24 | 72 |
| 1991 | 3.57 | 43 |