| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.69 | 91 |
| 2015 | 7.45 | 102 |
| 2014 | 7.95 | 105 |
| 2013 | 7.91 | 105 |
| 2012 | 8.23 | 109 |
| 2011 | 7.74 | 100 |
| 2010 | 6.5 | 68 |
| 2009 | 5.9 | 63 |
| 2008 | 5.6 | 70 |
| 2007 | 7.2 | 100 |
| 2006 | 3.2 | 26 |
| 2005 | 3.3 | 25 |
| 2004 | 3.6 | 28 |
| 2003 | 6.8 | 73 |
| 2002 | 6.2 | 65 |
| 2001 | 4.6 | 46 |
| 2000 | 4.6 | 47 |
| 1999 | 4.7 | 44 |
| 1998 | 5.9 | 62 |
| 1997 | 7.7 | 90 |
| 1996 | 6.7 | 73 |
| 1995 | 5.5 | 58 |
| 1994 | 9 | 110 |
| 1993 | 8.6 | 103 |
| 1992 | 7.66 | 94 |
| 1991 | 6.78 | 84 |