| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 6.57 | 93 |
| 2014 | 8.94 | 79 |
| 2013 | 9.5 | 84 |
| 2012 | 7.82 | 96 |
| 2011 | 9.84 | 88 |
| 2010 | 7.38 | 114 |
| 2009 | 5.23 | 117 |
| 2008 | 4.22 | 142 |
| 2007 | 18.82 | 77 |
| 2006 | 16.22 | 94 |
| 2005 | 3.54 | 153 |
| 2004 | 7.34 | 125 |
| 2003 | 6.28 | 121 |
| 2002 | 0.55 | 144 |
| 2001 | -.28 | 148 |
| 2000 | 9.33 | 106 |
| 1999 | 8.3 | 117 |
| 1998 | 11.13 | 82 |
| 1997 | 8.72 | 112 |
| 1996 | 12.49 | 89 |
| 1995 | 10.65 | 94 |
| 1994 | 11.74 | 97 |
| 1993 | 14.46 | 78 |
| 1992 | 8.48 | 92 |