| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 7.4 | 26 |
| 2014 | 6.08 | 37 |
| 2013 | 5.83 | 44 |
| 2012 | 6.36 | 48 |
| 2011 | 9.48 | 33 |
| 2010 | 9.25 | 21 |
| 2009 | 8.96 | 27 |
| 2008 | 9.22 | 83 |
| 2007 | 10.3 | 24 |
| 2006 | 10.77 | 26 |
| 2005 | 18.51 | 6 |
| 2004 | 13.81 | 14 |
| 2003 | -1.22 | 165 |
| 2002 | 15.93 | 15 |
| 2001 | 6.94 | 46 |
| 2000 | 11.86 | 28 |
| 1999 | 9.93 | 35 |
| 1998 | 6.21 | 75 |
| 1997 | 4.49 | 92 |
| 1996 | 19.76 | 41 |
| 1995 | 49.08 | 24 |
| 1994 | 38.94 | 31 |
| 1993 | 10.01 | 66 |
| 1992 | 14.51 | 47 |
| 1991 | 8.59 | 76 |
| 1990 | 11.78 | 54 |
| 1989 | 9.01 | 58 |
| 1988 | 26.85 | 26 |
| 1987 | 14.99 | 36 |
| 1986 | 14.5 | 37 |