| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.57 | 87 |
| 2015 | 6.21 | 79 |
| 2014 | 6.39 | 80 |
| 2013 | 5.93 | 72 |
| 2012 | 6.43 | 77 |
| 2011 | 7.12 | 89 |
| 2010 | 8.14 | 101 |
| 2009 | 9.69 | 129 |
| 2008 | 7.8 | 116 |
| 2007 | 7.14 | 98 |
| 2006 | 7.69 | 104 |
| 2005 | 8 | 101 |
| 2004 | 8.81 | 109 |
| 2003 | 8.5 | 100 |
| 2002 | 8.94 | 100 |
| 2001 | 9.13 | 110 |
| 2000 | 9.16 | 109 |
| 1999 | 9.81 | 113 |
| 1998 | 6.34 | 66 |
| 1997 | 6.12 | 64 |
| 1996 | 6.33 | 65 |
| 1995 | 4.7 | 47 |
| 1994 | 5.9 | 64 |
| 1993 | 4.5 | 51 |
| 1992 | 4.4 | 50 |
| 1991 | 5.3 | 57 |