| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.89 | 76 |
| 2015 | 5.61 | 70 |
| 2014 | 5.27 | 61 |
| 2013 | 5.3 | 61 |
| 2012 | 6.74 | 82 |
| 2011 | 7.42 | 96 |
| 2010 | 8 | 98 |
| 2009 | 8.2 | 102 |
| 2008 | 6.2 | 82 |
| 2007 | 5 | 56 |
| 2006 | 5.3 | 59 |
| 2005 | 5.6 | 61 |
| 2004 | 6.7 | 71 |
| 2003 | 8 | 91 |
| 2002 | 12.2 | 136 |
| 2001 | 6.4 | 68 |
| 2000 | 9.8 | 114 |
| 1999 | 10.9 | 116 |
| 1998 | 13.2 | 142 |
| 1997 | 13.3 | 141 |
| 1996 | 14.9 | 153 |
| 1995 | 16.9 | 159 |
| 1994 | 12.46 | 134 |
| 1993 | 13.4 | 141 |
| 1992 | 14.4 | 145 |
| 1991 | 14.45 | 147 |