| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.36 | 63 |
| 2015 | 4.77 | 51 |
| 2014 | 3.8 | 38 |
| 2013 | 4.15 | 44 |
| 2012 | 4.12 | 44 |
| 2011 | 4.21 | 43 |
| 2010 | 5.02 | 49 |
| 2009 | 6.47 | 69 |
| 2008 | 7.3 | 107 |
| 2007 | 6.1 | 77 |
| 2006 | 7.69 | 105 |
| 2005 | 7.74 | 96 |
| 2004 | 8.55 | 106 |
| 2003 | 11.44 | 131 |
| 2002 | 9.07 | 101 |
| 2001 | 10.71 | 125 |
| 2000 | 9 | 107 |
| 1999 | 14.4 | 152 |
| 1998 | 11.49 | 127 |
| 1997 | 9.17 | 105 |
| 1996 | 10.38 | 118 |
| 1995 | 6.9 | 77 |
| 1994 | 7.1 | 81 |
| 1993 | 8.3 | 99 |
| 1992 | 8.9 | 106 |
| 1991 | 5.8 | 68 |