| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 8.09 | 109 |
| 2015 | 9.4 | 125 |
| 2014 | 11.26 | 136 |
| 2013 | 13.04 | 145 |
| 2012 | 14.67 | 155 |
| 2011 | 14.63 | 154 |
| 2010 | 13.85 | 151 |
| 2009 | 12.01 | 141 |
| 2008 | 6.4 | 86 |
| 2007 | 4.67 | 53 |
| 2006 | 4.41 | 46 |
| 2005 | 4.34 | 37 |
| 2004 | 4.49 | 45 |
| 2003 | 4.48 | 41 |
| 2002 | 4.22 | 38 |
| 2001 | 3.68 | 31 |
| 2000 | 4.32 | 40 |
| 1999 | 5.8 | 56 |
| 1998 | 7.7 | 90 |
| 1997 | 10.2 | 117 |
| 1996 | 11.72 | 129 |
| 1995 | 11.98 | 136 |
| 1994 | 14.57 | 145 |
| 1993 | 15.59 | 149 |
| 1992 | 15.03 | 150 |
| 1991 | 15.77 | 152 |