| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.11 | 7 |
| 2015 | 6.55 | 18 |
| 2014 | 6.06 | 30 |
| 2013 | 6.01 | 36 |
| 2012 | 6.52 | 34 |
| 2011 | 6.46 | 46 |
| 2010 | 5.57 | 73 |
| 2009 | 5.05 | 30 |
| 2008 | 6.01 | 64 |
| 2007 | 7.06 | 67 |
| 2006 | 6.67 | 74 |
| 2005 | 6.54 | 61 |
| 2004 | 5.24 | 94 |
| 2003 | 4.74 | 81 |
| 2002 | 3.83 | 84 |
| 2001 | 5.08 | 49 |
| 2000 | 5.29 | 75 |
| 1999 | 4.67 | 56 |
| 1998 | 5.18 | 52 |
| 1997 | 4.49 | 92 |
| 1996 | 4.52 | 88 |
| 1995 | 5.12 | 67 |
| 1994 | 3.89 | 87 |
| 1993 | 4.71 | 57 |
| 1992 | 5.44 | 51 |
| 1991 | 3.49 | 67 |
| 1990 | 5.62 | 45 |
| 1989 | 2.84 | 103 |
| 1988 | 2.42 | 116 |
| 1987 | 3.77 | 72 |
| 1986 | 4.17 | 68 |