| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 69 | 37 |
| 2015 | 69.5 | 33 |
| 2014 | 70 | 29 |
| 2013 | 70.4 | 23 |
| 2012 | 70.8 | 21 |
| 2011 | 71.1 | 18 |
| 2010 | 71.3 | 16 |
| 2009 | 71.3 | 15 |
| 2008 | 71.2 | 15 |
| 2007 | 70.9 | 16 |
| 2006 | 70.6 | 16 |
| 2005 | 70.3 | 17 |
| 2004 | 69.9 | 17 |
| 2003 | 69.6 | 17 |
| 2002 | 69.2 | 18 |
| 2001 | 68.9 | 16 |
| 2000 | 68.4 | 18 |
| 1999 | 67.9 | 27 |
| 1998 | 67.3 | 36 |
| 1997 | 66.8 | 39 |
| 1996 | 66.3 | 45 |
| 1995 | 66 | 46 |
| 1994 | 65.6 | 49 |
| 1993 | 65.4 | 53 |
| 1992 | 65.2 | 54 |
| 1991 | 65.1 | 56 |
| 1990 | 64.9 | 56 |
| 1989 | 64.9 | 52 |
| 1988 | 64.9 | 52 |
| 1987 | 64.9 | 50 |
| 1986 | 65 | 48 |