| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 66.7 | 63 |
| 2015 | 67.3 | 56 |
| 2014 | 67.8 | 52 |
| 2013 | 68.2 | 49 |
| 2012 | 68.7 | 43 |
| 2011 | 69 | 36 |
| 2010 | 69.2 | 36 |
| 2009 | 69.2 | 35 |
| 2008 | 69 | 34 |
| 2007 | 68.7 | 38 |
| 2006 | 68.1 | 40 |
| 2005 | 67.3 | 47 |
| 2004 | 66.3 | 65 |
| 2003 | 65.1 | 77 |
| 2002 | 63.8 | 87 |
| 2001 | 62.6 | 92 |
| 2000 | 61.5 | 98 |
| 1999 | 60.5 | 100 |
| 1998 | 59.7 | 104 |
| 1997 | 59.1 | 107 |
| 1996 | 58.4 | 108 |
| 1995 | 57.6 | 108 |
| 1994 | 57 | 110 |
| 1993 | 56.5 | 112 |
| 1992 | 56 | 112 |
| 1991 | 55.6 | 115 |
| 1990 | 55.4 | 115 |
| 1989 | 54.9 | 116 |
| 1988 | 54.4 | 120 |
| 1987 | 54.1 | 121 |
| 1986 | 53.8 | 124 |