| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.82 | 73 |
| 2015 | 5.35 | 64 |
| 2014 | 4.82 | 49 |
| 2013 | 4.1 | 42 |
| 2012 | 4.05 | 40 |
| 2011 | 4.48 | 47 |
| 2010 | 6.5 | 69 |
| 2009 | 6.6 | 73 |
| 2008 | 5.6 | 69 |
| 2007 | 6.4 | 80 |
| 2006 | 8.7 | 116 |
| 2005 | 9.8 | 124 |
| 2004 | 11.7 | 138 |
| 2003 | 13 | 144 |
| 2002 | 13.5 | 144 |
| 2001 | 14 | 149 |
| 2000 | 13.5 | 142 |
| 1999 | 11.8 | 129 |
| 1998 | 14 | 149 |
| 1997 | 13.4 | 142 |
| 1996 | 14.5 | 149 |
| 1995 | 14 | 147 |
| 1994 | 14 | 142 |
| 1993 | 13.3 | 140 |
| 1992 | 14.7 | 146 |
| 1991 | 16.1 | 155 |