| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 0.67 | 119 |
| 2015 | 0.71 | 128 |
| 2014 | 0.77 | 130 |
| 2013 | 0.81 | 128 |
| 2012 | 0.87 | 125 |
| 2011 | 1.09 | 103 |
| 2010 | 1.13 | 103 |
| 2009 | 1.18 | 106 |
| 2008 | 1.49 | 81 |
| 2007 | 1.86 | 60 |
| 2006 | 2.27 | 46 |
| 2005 | 2.76 | 33 |
| 2004 | 3.08 | 26 |
| 2003 | 3.24 | 31 |
| 2002 | 3.69 | 24 |
| 2001 | 4.32 | 16 |
| 2000 | 7.56 | 4 |
| 1999 | 9.66 | 5 |
| 1998 | 6.06 | 10 |
| 1997 | 2.71 | 45 |
| 1996 | 1.49 | 92 |
| 1995 | 1.57 | 89 |
| 1994 | 2.03 | 69 |
| 1993 | 2.17 | 68 |
| 1992 | 2.43 | 60 |
| 1991 | 3.93 | 29 |
| 1990 | 6.45 | 17 |
| 1989 | 6.81 | 13 |
| 1988 | 5.64 | 16 |
| 1987 | 4.53 | 23 |
| 1986 | 4.46 | 23 |