| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 85 | 1 |
| 2015 | 85.2 | 1 |
| 2014 | 85.3 | 1 |
| 2013 | 85.4 | 2 |
| 2012 | 85.5 | 2 |
| 2011 | 85.6 | 2 |
| 2010 | 85.9 | 1 |
| 2009 | 85.4 | 1 |
| 2008 | 84.7 | 1 |
| 2007 | 83.8 | 1 |
| 2006 | 82.4 | 1 |
| 2005 | 80.7 | 1 |
| 2004 | 79.7 | 1 |
| 2003 | 78.5 | 1 |
| 2002 | 77 | 1 |
| 2001 | 75.1 | 1 |
| 2000 | 72.9 | 1 |
| 1999 | 72.8 | 1 |
| 1998 | 72.7 | 1 |
| 1997 | 72.4 | 1 |
| 1996 | 72.1 | 1 |
| 1995 | 71.7 | 1 |
| 1994 | 71 | 4 |
| 1993 | 70.2 | 5 |
| 1992 | 69.4 | 6 |
| 1991 | 68.6 | 14 |
| 1990 | 67.9 | 20 |
| 1989 | 67.4 | 22 |
| 1988 | 67.1 | 24 |
| 1987 | 66.8 | 27 |
| 1986 | 66.8 | 27 |