| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 68.6 | 44 |
| 2015 | 69.1 | 39 |
| 2014 | 69.4 | 34 |
| 2013 | 69.7 | 32 |
| 2012 | 69.8 | 30 |
| 2011 | 70 | 29 |
| 2010 | 70.2 | 27 |
| 2009 | 70.1 | 25 |
| 2008 | 70 | 22 |
| 2007 | 69.8 | 22 |
| 2006 | 69.6 | 22 |
| 2005 | 69.5 | 21 |
| 2004 | 69.3 | 20 |
| 2003 | 69.3 | 19 |
| 2002 | 69.3 | 17 |
| 2001 | 69.2 | 14 |
| 2000 | 69.1 | 13 |
| 1999 | 68.6 | 13 |
| 1998 | 68.1 | 20 |
| 1997 | 67.4 | 29 |
| 1996 | 66.9 | 37 |
| 1995 | 66.6 | 37 |
| 1994 | 66.4 | 40 |
| 1993 | 66.3 | 40 |
| 1992 | 66.5 | 31 |
| 1991 | 66.6 | 29 |
| 1990 | 66.8 | 27 |
| 1989 | 66.9 | 26 |
| 1988 | 66.9 | 26 |
| 1987 | 66.9 | 23 |
| 1986 | 66.9 | 24 |