| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.9 | 97 |
| 2015 | 6.82 | 93 |
| 2014 | 6.95 | 97 |
| 2013 | 7.79 | 104 |
| 2012 | 7.41 | 97 |
| 2011 | 7.84 | 104 |
| 2010 | 8.45 | 108 |
| 2009 | 8.05 | 99 |
| 2008 | 6.85 | 96 |
| 2007 | 7.47 | 107 |
| 2006 | 9.33 | 126 |
| 2005 | 11.4 | 143 |
| 2004 | 15 | 156 |
| 2003 | 16.8 | 163 |
| 2002 | 16.2 | 159 |
| 2001 | 12.8 | 141 |
| 2000 | 13.2 | 139 |
| 1999 | 14.5 | 153 |
| 1998 | 11 | 124 |
| 1997 | 10.6 | 122 |
| 1996 | 12.4 | 135 |
| 1995 | 10.2 | 123 |
| 1994 | 8.6 | 104 |
| 1993 | 6.7 | 81 |
| 1992 | 7.7 | 96 |
| 1991 | 9.5 | 115 |