| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 9.22 | 71 |
| 2015 | 8.9 | 71 |
| 2014 | 8.56 | 72 |
| 2013 | 8.21 | 72 |
| 2012 | 7.87 | 73 |
| 2011 | 7.55 | 74 |
| 2010 | 7.27 | 75 |
| 2009 | 7.05 | 77 |
| 2008 | 6.87 | 79 |
| 2007 | 6.73 | 81 |
| 2006 | 6.58 | 81 |
| 2005 | 6.41 | 83 |
| 2004 | 6.24 | 83 |
| 2003 | 6.04 | 83 |
| 2002 | 5.81 | 85 |
| 2001 | 5.58 | 88 |
| 2000 | 5.35 | 89 |
| 1999 | 5.2 | 89 |
| 1998 | 5.06 | 89 |
| 1997 | 4.93 | 90 |
| 1996 | 4.79 | 92 |
| 1995 | 4.65 | 94 |
| 1994 | 4.53 | 96 |
| 1993 | 4.39 | 98 |
| 1992 | 4.25 | 98 |
| 1991 | 4.11 | 103 |
| 1990 | 3.97 | 108 |
| 1989 | 3.83 | 110 |
| 1988 | 3.71 | 118 |
| 1987 | 3.61 | 121 |
| 1986 | 3.52 | 123 |