| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 78 | 3 |
| 2015 | 79 | 3 |
| 2014 | 79.6 | 3 |
| 2013 | 80.1 | 3 |
| 2012 | 80.4 | 3 |
| 2011 | 80.5 | 3 |
| 2010 | 80.5 | 3 |
| 2009 | 79.9 | 3 |
| 2008 | 79.2 | 3 |
| 2007 | 78.3 | 3 |
| 2006 | 77.2 | 3 |
| 2005 | 76 | 3 |
| 2004 | 74.7 | 3 |
| 2003 | 73.4 | 3 |
| 2002 | 72 | 5 |
| 2001 | 70.8 | 6 |
| 2000 | 69.8 | 9 |
| 1999 | 69 | 11 |
| 1998 | 68.5 | 14 |
| 1997 | 68 | 20 |
| 1996 | 67.6 | 24 |
| 1995 | 67.4 | 27 |
| 1994 | 67.2 | 27 |
| 1993 | 67.2 | 24 |
| 1992 | 67.5 | 21 |
| 1991 | 67.7 | 21 |
| 1990 | 67.9 | 19 |
| 1989 | 68.2 | 16 |
| 1988 | 68.3 | 13 |
| 1987 | 68.2 | 14 |
| 1986 | 68.4 | 12 |