| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 70 | 23 |
| 2015 | 70.3 | 23 |
| 2014 | 70.4 | 22 |
| 2013 | 70.6 | 22 |
| 2012 | 70.7 | 24 |
| 2011 | 70.7 | 23 |
| 2010 | 70.7 | 20 |
| 2009 | 70.5 | 21 |
| 2008 | 70.2 | 19 |
| 2007 | 69.9 | 21 |
| 2006 | 69.5 | 23 |
| 2005 | 69.2 | 22 |
| 2004 | 68.9 | 25 |
| 2003 | 68.5 | 28 |
| 2002 | 68.1 | 31 |
| 2001 | 67.7 | 37 |
| 2000 | 67.4 | 41 |
| 1999 | 66.9 | 45 |
| 1998 | 66.5 | 48 |
| 1997 | 66 | 50 |
| 1996 | 65.7 | 51 |
| 1995 | 65.5 | 51 |
| 1994 | 65.2 | 54 |
| 1993 | 65 | 56 |
| 1992 | 64.9 | 59 |
| 1991 | 64.7 | 58 |
| 1990 | 64.6 | 58 |
| 1989 | 64.8 | 53 |
| 1988 | 64.9 | 51 |
| 1987 | 65 | 48 |
| 1986 | 65.1 | 47 |