| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 7.76 | 85 |
| 2014 | 7.47 | 89 |
| 2013 | 7.32 | 94 |
| 2012 | 7.36 | 94 |
| 2011 | 7.71 | 94 |
| 2010 | 7.46 | 95 |
| 2009 | 8.07 | 93 |
| 2008 | 7.8 | 94 |
| 2007 | 7.31 | 98 |
| 2006 | 7.22 | 98 |
| 2005 | 7.53 | 97 |
| 2004 | 7.62 | 97 |
| 2003 | 8.02 | 96 |
| 2002 | 8.23 | 97 |
| 2001 | 8.63 | 95 |
| 2000 | 8.85 | 92 |
| 1999 | 9.09 | 92 |
| 1998 | 9.27 | 93 |
| 1997 | 8.9 | 97 |
| 1996 | 9.4 | 93 |
| 1995 | 8.93 | 98 |
| 1994 | 9.32 | 91 |
| 1993 | 9.13 | 90 |
| 1992 | 8.6 | 94 |
| 1991 | 8.54 | 92 |