| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.09 | 100 |
| 2015 | 7.43 | 101 |
| 2014 | 7.95 | 106 |
| 2013 | 8.05 | 106 |
| 2012 | 7.98 | 105 |
| 2011 | 7.8 | 103 |
| 2010 | 8.61 | 111 |
| 2009 | 8.35 | 107 |
| 2008 | 6.24 | 84 |
| 2007 | 6.16 | 78 |
| 2006 | 7.07 | 92 |
| 2005 | 7.49 | 90 |
| 2004 | 6.69 | 70 |
| 2003 | 5.55 | 54 |
| 2002 | 4.97 | 47 |
| 2001 | 4.73 | 50 |
| 2000 | 5.47 | 59 |
| 1999 | 7.61 | 89 |
| 1998 | 8.94 | 103 |
| 1997 | 10.36 | 119 |
| 1996 | 9.55 | 108 |
| 1995 | 8.9 | 108 |
| 1994 | 9.58 | 114 |
| 1993 | 9.33 | 109 |
| 1992 | 5.72 | 66 |
| 1991 | 3.24 | 38 |