| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 1.96 | 99 |
| 2015 | 2.13 | 92 |
| 2014 | 2.28 | 87 |
| 2013 | 2.5 | 76 |
| 2012 | 2.64 | 74 |
| 2011 | 2.84 | 71 |
| 2010 | 2.95 | 70 |
| 2009 | 3.09 | 60 |
| 2008 | 3.46 | 53 |
| 2007 | 4.13 | 34 |
| 2006 | 5.03 | 15 |
| 2005 | 6.16 | 8 |
| 2004 | 7.35 | 3 |
| 2003 | 8.09 | 1 |
| 2002 | 8.19 | 2 |
| 2001 | 7.68 | 2 |
| 2000 | 6.51 | 4 |
| 1999 | 5.34 | 10 |
| 1998 | 4.61 | 18 |
| 1997 | 4.64 | 22 |
| 1996 | 5.29 | 8 |
| 1995 | 6.23 | 5 |
| 1994 | 7.07 | 4 |
| 1993 | 7.58 | 4 |
| 1992 | 7.58 | 5 |
| 1991 | 7.1 | 5 |
| 1990 | 6.96 | 7 |
| 1989 | 6.43 | 14 |
| 1988 | 5.99 | 18 |
| 1987 | 6.2 | 20 |
| 1986 | 6.67 | 18 |