| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 8.15 | 111 |
| 2015 | 7.3 | 99 |
| 2014 | 6.46 | 82 |
| 2013 | 6.45 | 80 |
| 2012 | 6.44 | 78 |
| 2011 | 6.32 | 70 |
| 2010 | 6.8 | 76 |
| 2009 | 7.3 | 88 |
| 2008 | 7.7 | 112 |
| 2007 | 9.15 | 131 |
| 2006 | 10.56 | 137 |
| 2005 | 12.2 | 148 |
| 2004 | 15.23 | 157 |
| 2003 | 16.35 | 158 |
| 2002 | 17 | 162 |
| 2001 | 14.9 | 153 |
| 2000 | 13.33 | 140 |
| 1999 | 11.3 | 120 |
| 1998 | 9.78 | 114 |
| 1997 | 11.4 | 127 |
| 1996 | 10.85 | 120 |
| 1995 | 10.02 | 121 |
| 1994 | 9.04 | 111 |
| 1993 | 8.35 | 100 |
| 1992 | 8.96 | 108 |
| 1991 | 8.95 | 107 |