| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 70.3 | 21 |
| 2015 | 70.6 | 22 |
| 2014 | 70.8 | 19 |
| 2013 | 70.8 | 19 |
| 2012 | 70.8 | 20 |
| 2011 | 70.7 | 22 |
| 2010 | 70.5 | 23 |
| 2009 | 70.2 | 23 |
| 2008 | 69.9 | 25 |
| 2007 | 69.5 | 26 |
| 2006 | 69.1 | 29 |
| 2005 | 68.8 | 33 |
| 2004 | 68.5 | 33 |
| 2003 | 68.2 | 34 |
| 2002 | 68 | 34 |
| 2001 | 67.7 | 38 |
| 2000 | 67.4 | 38 |
| 1999 | 67.1 | 40 |
| 1998 | 66.8 | 43 |
| 1997 | 66.6 | 44 |
| 1996 | 66.3 | 44 |
| 1995 | 66.2 | 44 |
| 1994 | 66.2 | 44 |
| 1993 | 66.3 | 41 |
| 1992 | 66.4 | 36 |
| 1991 | 66.5 | 31 |
| 1990 | 66.6 | 31 |
| 1989 | 66.6 | 30 |
| 1988 | 66.6 | 32 |
| 1987 | 66.6 | 29 |
| 1986 | 66.5 | 29 |