| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 68.7 | 43 |
| 2015 | 68.7 | 43 |
| 2014 | 68.7 | 42 |
| 2013 | 68.7 | 40 |
| 2012 | 68.5 | 46 |
| 2011 | 68.4 | 47 |
| 2010 | 68.3 | 48 |
| 2009 | 68.1 | 49 |
| 2008 | 67.9 | 50 |
| 2007 | 67.7 | 50 |
| 2006 | 67.5 | 49 |
| 2005 | 67.2 | 52 |
| 2004 | 66.9 | 55 |
| 2003 | 66.5 | 57 |
| 2002 | 66.1 | 59 |
| 2001 | 65.7 | 60 |
| 2000 | 65.4 | 61 |
| 1999 | 65.1 | 63 |
| 1998 | 64.9 | 62 |
| 1997 | 64.7 | 62 |
| 1996 | 64.5 | 64 |
| 1995 | 64.3 | 65 |
| 1994 | 64.2 | 64 |
| 1993 | 64 | 63 |
| 1992 | 63.9 | 63 |
| 1991 | 63.8 | 64 |
| 1990 | 63.8 | 65 |
| 1989 | 63.6 | 63 |
| 1988 | 63.5 | 62 |
| 1987 | 63.3 | 61 |
| 1986 | 63.1 | 61 |