| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 73 | 8 |
| 2015 | 73.6 | 8 |
| 2014 | 74.2 | 8 |
| 2013 | 74.7 | 6 |
| 2012 | 75 | 6 |
| 2011 | 75.1 | 6 |
| 2010 | 75.1 | 5 |
| 2009 | 75 | 5 |
| 2008 | 74.7 | 5 |
| 2007 | 74.3 | 5 |
| 2006 | 73.8 | 4 |
| 2005 | 73.4 | 4 |
| 2004 | 73.1 | 4 |
| 2003 | 72.8 | 4 |
| 2002 | 72.6 | 3 |
| 2001 | 72.4 | 3 |
| 2000 | 72.1 | 4 |
| 1999 | 72 | 4 |
| 1998 | 71.8 | 3 |
| 1997 | 71.6 | 3 |
| 1996 | 71.4 | 3 |
| 1995 | 71.3 | 3 |
| 1994 | 71.2 | 2 |
| 1993 | 71 | 3 |
| 1992 | 70.9 | 3 |
| 1991 | 70.7 | 3 |
| 1990 | 70.4 | 2 |
| 1989 | 70.2 | 2 |
| 1988 | 70 | 2 |
| 1987 | 69.7 | 2 |
| 1986 | 69.4 | 5 |