| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.88 | 75 |
| 2015 | 6.29 | 80 |
| 2014 | 6.59 | 86 |
| 2013 | 7.1 | 92 |
| 2012 | 6.99 | 92 |
| 2011 | 7.03 | 88 |
| 2010 | 7.35 | 90 |
| 2009 | 7.47 | 92 |
| 2008 | 7.33 | 108 |
| 2007 | 7.39 | 102 |
| 2006 | 7.98 | 108 |
| 2005 | 7.74 | 97 |
| 2004 | 11.85 | 141 |
| 2003 | 11.39 | 130 |
| 2002 | 11.51 | 129 |
| 2001 | 10.95 | 129 |
| 2000 | 11.19 | 127 |
| 1999 | 9.43 | 111 |
| 1998 | 9.38 | 111 |
| 1997 | 7.85 | 92 |
| 1996 | 7.41 | 86 |
| 1995 | 8.36 | 98 |
| 1994 | 8.43 | 100 |
| 1993 | 8.87 | 106 |
| 1992 | 8.64 | 104 |
| 1991 | 8.99 | 111 |