| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 7.48 | 35 |
| 2014 | 5.55 | 52 |
| 2013 | 7.49 | 30 |
| 2012 | 6.79 | 48 |
| 2011 | 4.73 | 71 |
| 2010 | 8.53 | 36 |
| 2009 | 4.53 | 69 |
| 2008 | 5.24 | 84 |
| 2007 | 9.42 | 50 |
| 2006 | 4.83 | 85 |
| 2005 | 4.28 | 79 |
| 2004 | 5.85 | 46 |
| 2003 | 7.08 | 31 |
| 2002 | 7.11 | 21 |
| 2001 | 3.54 | 67 |
| 2000 | 3.38 | 85 |
| 1999 | 4.76 | 56 |
| 1998 | 5.6 | 38 |
| 1997 | 4.82 | 38 |
| 1996 | 3.26 | 40 |
| 1995 | 2.55 | 54 |
| 1994 | 1.09 | 84 |
| 1993 | 9.61 | 7 |
| 1992 | 1.41 | 53 |
| 1991 | 1.02 | 67 |
| 1990 | 6.17 | 10 |
| 1989 | 4.09 | 19 |
| 1988 | 2.51 | 23 |
| 1987 | 3.28 | 17 |
| 1986 | 1.7 | 24 |