| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.4 | 76 |
| 2015 | 7.23 | 76 |
| 2014 | 7.11 | 75 |
| 2013 | 6.99 | 75 |
| 2012 | 6.87 | 74 |
| 2011 | 6.77 | 71 |
| 2010 | 6.68 | 69 |
| 2009 | 6.5 | 68 |
| 2008 | 6.34 | 66 |
| 2007 | 6.19 | 61 |
| 2006 | 6.02 | 53 |
| 2005 | 5.85 | 48 |
| 2004 | 5.8 | 44 |
| 2003 | 5.76 | 40 |
| 2002 | 5.71 | 38 |
| 2001 | 5.65 | 33 |
| 2000 | 5.59 | 33 |
| 1999 | 5.56 | 30 |
| 1998 | 5.52 | 30 |
| 1997 | 5.47 | 27 |
| 1996 | 5.43 | 25 |
| 1995 | 5.4 | 25 |
| 1994 | 5.42 | 23 |
| 1993 | 5.47 | 26 |
| 1992 | 5.53 | 28 |
| 1991 | 5.59 | 34 |
| 1990 | 5.62 | 37 |
| 1989 | 5.68 | 36 |
| 1988 | 5.72 | 38 |
| 1987 | 5.74 | 39 |
| 1986 | 5.75 | 39 |