| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 4.3 | 92 |
| 2015 | 4.17 | 110 |
| 2014 | 3.78 | 119 |
| 2013 | 3.4 | 128 |
| 2012 | 3.13 | 128 |
| 2011 | 3.33 | 128 |
| 2010 | 3.42 | 125 |
| 2009 | 3.05 | 129 |
| 2008 | 2.7 | 134 |
| 2007 | 2.84 | 134 |
| 2006 | 2.95 | 136 |
| 2005 | 3.09 | 136 |
| 2004 | 2.81 | 140 |
| 2003 | 2.83 | 141 |
| 2002 | 2.55 | 144 |
| 2001 | 2.27 | 148 |
| 2000 | 2.35 | 145 |
| 1999 | 2.38 | 143 |
| 1998 | 3.07 | 136 |
| 1997 | 3.33 | 139 |
| 1996 | 3.83 | 134 |
| 1995 | 4.32 | 130 |
| 1994 | 5.23 | 110 |
| 1993 | 5.98 | 104 |
| 1992 | 7.89 | 95 |
| 1991 | 8.14 | 94 |
| 1990 | 7.71 | 99 |
| 1989 | 6.03 | 94 |
| 1988 | 6.67 | 90 |
| 1987 | 6.74 | 89 |
| 1986 | 5.9 | 88 |