| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 3.2 | 32 |
| 2015 | 1.69 | 127 |
| 2014 | 3.48 | 79 |
| 2013 | 3.11 | 94 |
| 2012 | 4.68 | 68 |
| 2011 | 6.44 | 51 |
| 2010 | 5.72 | 54 |
| 2009 | 8.79 | 32 |
| 2008 | 8.09 | 54 |
| 2007 | 7.25 | 72 |
| 2006 | 7.31 | 57 |
| 2005 | 5.96 | 55 |
| 2004 | 6.91 | 40 |
| 2003 | 4.38 | 54 |
| 2002 | 4.66 | 48 |
| 2001 | 3.3 | 73 |
| 2000 | 5.45 | 46 |
| 1999 | 6.61 | 38 |
| 1998 | 11.66 | 10 |
| 1997 | 3.17 | 62 |
| 1996 | 1.1 | 102 |
| 1995 | 1.72 | 72 |
| 1994 | 0.61 | 106 |
| 1993 | 0.07 | 131 |
| 1992 | 0.19 | 112 |