| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 3.7 | 65 |
| 2015 | 3.76 | 71 |
| 2014 | 3.79 | 83 |
| 2013 | 2.77 | 108 |
| 2012 | 3.37 | 99 |
| 2011 | 2.89 | 116 |
| 2010 | 3.63 | 108 |
| 2009 | 1.63 | 80 |
| 2008 | 2.36 | 131 |
| 2007 | 3.37 | 147 |
| 2006 | 1.68 | 183 |
| 2005 | 5.91 | 76 |
| 2004 | 4.3 | 125 |
| 2003 | 7.2 | 41 |
| 2002 | 5.61 | 41 |
| 2001 | 3.01 | 99 |
| 2000 | 3.82 | 116 |
| 1999 | 3.2 | 104 |
| 1998 | 5.1 | 54 |
| 1997 | 1.1 | 164 |
| 1996 | 4.1 | 101 |
| 1995 | 3.8 | 103 |
| 1994 | -.9 | 155 |
| 1993 | -2.1 | 156 |
| 1992 | 1.8 | 92 |
| 1991 | -1.2 | 143 |
| 1990 | 0.8 | 113 |
| 1989 | 4.4 | 65 |
| 1988 | -1 | 145 |
| 1987 | -.7 | 139 |
| 1986 | 0.4 | 126 |