| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 4.2 | 19 |
| 2015 | 4.33 | 20 |
| 2014 | 4.47 | 21 |
| 2013 | 4.65 | 17 |
| 2012 | 4.84 | 15 |
| 2011 | 5.58 | 9 |
| 2010 | 4.98 | 15 |
| 2009 | 2.66 | 74 |
| 2008 | 7.04 | 5 |
| 2007 | 8.25 | 3 |
| 2006 | 7.4 | 4 |
| 2005 | 6.65 | 4 |
| 2004 | 6.48 | 6 |
| 2003 | 6.28 | 7 |
| 2002 | 5.72 | 9 |
| 2001 | 6.15 | 6 |
| 2000 | 4.21 | 28 |
| 1999 | 4.67 | 18 |
| 1998 | 4.03 | 35 |
| 1997 | 2.18 | 99 |
| 1996 | 4.14 | 36 |
| 1995 | 4.2 | 32 |
| 1994 | 0.99 | 148 |
| 1993 | 3.11 | 78 |
| 1992 | 2.79 | 88 |
| 1991 | 3.8 | 65 |
| 1990 | 0.78 | 166 |
| 1989 | 3.45 | 82 |
| 1988 | 3.58 | 83 |
| 1987 | 3.69 | 87 |
| 1986 | 3.79 | 81 |