| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 4.66 | 46 |
| 2014 | 5.68 | 44 |
| 2013 | 5.2 | 59 |
| 2012 | 9.27 | 29 |
| 2011 | 5.1 | 83 |
| 2010 | 10.55 | 16 |
| 2009 | 6.97 | 42 |
| 2008 | 12.05 | 53 |
| 2007 | 7.89 | 55 |
| 2006 | 8.32 | 44 |
| 2005 | 6.89 | 61 |
| 2004 | 3.72 | 85 |
| 2003 | 3.81 | 78 |
| 2002 | 4.14 | 70 |
| 2001 | 5.54 | 61 |
| 2000 | 3.56 | 84 |
| 1999 | 3.44 | 78 |
| 1998 | 5.61 | 79 |
| 1997 | 3.63 | 101 |
| 1996 | 3.4 | 115 |
| 1995 | 5.18 | 111 |
| 1994 | 8.81 | 83 |
| 1993 | 10.84 | 62 |
| 1992 | 6.44 | 76 |
| 1991 | 3.78 | 106 |
| 1990 | 11.06 | 57 |
| 1989 | 11.43 | 52 |
| 1988 | 7.76 | 63 |
| 1987 | 10.75 | 46 |
| 1986 | 7.69 | 58 |