| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 66.3 | 72 |
| 2015 | 66 | 80 |
| 2014 | 65.8 | 89 |
| 2013 | 65.4 | 97 |
| 2012 | 65.1 | 103 |
| 2011 | 64.7 | 107 |
| 2010 | 64.3 | 109 |
| 2009 | 63.9 | 111 |
| 2008 | 63.5 | 110 |
| 2007 | 63.1 | 110 |
| 2006 | 62.7 | 111 |
| 2005 | 62.3 | 111 |
| 2004 | 62 | 110 |
| 2003 | 61.7 | 107 |
| 2002 | 61.4 | 107 |
| 2001 | 61 | 106 |
| 2000 | 60.7 | 105 |
| 1999 | 60.4 | 104 |
| 1998 | 60.1 | 102 |
| 1997 | 59.8 | 101 |
| 1996 | 59.5 | 100 |
| 1995 | 59.1 | 99 |
| 1994 | 58.7 | 100 |
| 1993 | 58.3 | 101 |
| 1992 | 57.8 | 103 |
| 1991 | 57.2 | 103 |
| 1990 | 56.7 | 105 |
| 1989 | 56.1 | 107 |
| 1988 | 55.4 | 111 |
| 1987 | 54.6 | 115 |
| 1986 | 53.9 | 122 |