| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 3.2 | 45 |
| 2015 | 3.27 | 64 |
| 2014 | 2.91 | 83 |
| 2013 | 2.7 | 91 |
| 2012 | 3.2 | 105 |
| 2011 | 4.91 | 93 |
| 2010 | 4.5 | 72 |
| 2009 | 4.61 | 64 |
| 2008 | 10.58 | 66 |
| 2007 | 5.48 | 84 |
| 2006 | 3.06 | 118 |
| 2005 | 4.14 | 90 |
| 2004 | 1.25 | 140 |
| 2003 | 0.96 | 144 |
| 2002 | 0.89 | 143 |
| 2001 | 1.3 | 147 |
| 2000 | 1.81 | 119 |
| 1999 | 2.99 | 85 |
| 1998 | 0.13 | 150 |
| 1997 | 0.68 | 153 |
| 1996 | 3.55 | 113 |
| 1995 | 2.69 | 128 |
| 1994 | 2.53 | 126 |
| 1993 | 0.38 | 144 |
| 1992 | -.55 | 134 |
| 1991 | 9.06 | 71 |
| 1990 | 9.83 | 62 |
| 1989 | 3.34 | 103 |
| 1988 | 1.47 | 112 |
| 1987 | 0.65 | 107 |
| 1986 | 0.95 | 106 |