| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2014 | 0.5 | 64 |
| 2013 | 0.4 | 66 |
| 2012 | 1.8 | 56 |
| 2011 | 0.9 | 64 |
| 2010 | 0.2 | 77 |
| 2009 | 0.1 | 74 |
| 2008 | 1.2 | 68 |
| 2007 | 1.7 | 64 |
| 2006 | 1.4 | 66 |
| 2005 | 1 | 65 |
| 2004 | 1.2 | 69 |
| 2003 | 0.4 | 72 |
| 2002 | 0.5 | 66 |
| 2001 | 0.4 | 72 |
| 2000 | 1.5 | 60 |
| 1999 | 0.5 | 69 |
| 1998 | 0.9 | 66 |
| 1997 | 0.5 | 72 |
| 1996 | 0.2 | 71 |
| 1995 | 0.1 | 71 |
| 1994 | 0.7 | 56 |
| 1993 | 0.7 | 49 |