| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 4.05 | 41 |
| 2015 | 5.05 | 56 |
| 2014 | 6.11 | 76 |
| 2013 | 6.95 | 87 |
| 2012 | 6.98 | 91 |
| 2011 | 6.71 | 77 |
| 2010 | 7.28 | 86 |
| 2009 | 6.66 | 75 |
| 2008 | 4.39 | 52 |
| 2007 | 5.32 | 63 |
| 2006 | 7.15 | 94 |
| 2005 | 7.93 | 99 |
| 2004 | 8.21 | 97 |
| 2003 | 7.54 | 82 |
| 2002 | 7.02 | 83 |
| 2001 | 7.99 | 99 |
| 2000 | 8.76 | 103 |
| 1999 | 8.49 | 100 |
| 1998 | 5.9 | 63 |
| 1997 | 4.27 | 41 |
| 1996 | 3.89 | 35 |
| 1995 | 4.02 | 40 |
| 1994 | 4.3 | 44 |
| 1993 | 4.32 | 48 |
| 1992 | 3.3 | 34 |
| 1991 | 2.27 | 21 |