| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 72.2 | 13 |
| 2015 | 72.6 | 11 |
| 2014 | 73 | 11 |
| 2013 | 73.3 | 11 |
| 2012 | 73.6 | 9 |
| 2011 | 73.7 | 7 |
| 2010 | 73.8 | 7 |
| 2009 | 73.7 | 7 |
| 2008 | 73.6 | 7 |
| 2007 | 73.3 | 7 |
| 2006 | 72.9 | 6 |
| 2005 | 72.4 | 6 |
| 2004 | 71.7 | 7 |
| 2003 | 70.8 | 8 |
| 2002 | 69.9 | 13 |
| 2001 | 69.1 | 15 |
| 2000 | 68.5 | 17 |
| 1999 | 67.8 | 28 |
| 1998 | 67.5 | 31 |
| 1997 | 67.2 | 34 |
| 1996 | 67 | 36 |
| 1995 | 66.4 | 43 |
| 1994 | 66.3 | 43 |
| 1993 | 66 | 45 |
| 1992 | 65.7 | 49 |
| 1991 | 65.5 | 50 |
| 1990 | 65.6 | 50 |
| 1989 | 65.3 | 51 |
| 1988 | 65.1 | 49 |
| 1987 | 64.8 | 51 |
| 1986 | 64.4 | 54 |