| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 9.23 | 93 |
| 2015 | 8.91 | 93 |
| 2014 | 8.6 | 92 |
| 2013 | 8.28 | 91 |
| 2012 | 7.95 | 88 |
| 2011 | 7.63 | 88 |
| 2010 | 7.3 | 79 |
| 2009 | 7.11 | 75 |
| 2008 | 6.92 | 72 |
| 2007 | 6.71 | 69 |
| 2006 | 6.51 | 68 |
| 2005 | 6.29 | 66 |
| 2004 | 6.11 | 58 |
| 2003 | 5.95 | 50 |
| 2002 | 5.81 | 42 |
| 2001 | 5.69 | 35 |
| 2000 | 5.58 | 31 |
| 1999 | 5.47 | 27 |
| 1998 | 5.36 | 23 |
| 1997 | 5.25 | 19 |
| 1996 | 5.13 | 16 |
| 1995 | 5 | 15 |
| 1994 | 5.03 | 13 |
| 1993 | 5.05 | 12 |
| 1992 | 5.05 | 12 |
| 1991 | 5.03 | 14 |
| 1990 | 5 | 14 |
| 1989 | 5 | 14 |
| 1988 | 4.97 | 14 |
| 1987 | 4.92 | 14 |
| 1986 | 4.85 | 14 |