| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 65.2 | 96 |
| 2015 | 64.9 | 104 |
| 2014 | 64.5 | 107 |
| 2013 | 64.1 | 112 |
| 2012 | 63.5 | 119 |
| 2011 | 63 | 121 |
| 2010 | 62.5 | 122 |
| 2009 | 62 | 123 |
| 2008 | 61.5 | 123 |
| 2007 | 61 | 122 |
| 2006 | 60.4 | 121 |
| 2005 | 59.8 | 122 |
| 2004 | 59.2 | 123 |
| 2003 | 58.6 | 124 |
| 2002 | 57.9 | 125 |
| 2001 | 57.2 | 125 |
| 2000 | 56.5 | 127 |
| 1999 | 55.9 | 127 |
| 1998 | 55.2 | 129 |
| 1997 | 54.6 | 133 |
| 1996 | 53.9 | 137 |
| 1995 | 53.3 | 141 |
| 1994 | 52.8 | 146 |
| 1993 | 52.3 | 149 |
| 1992 | 51.9 | 156 |
| 1991 | 51.4 | 160 |
| 1990 | 51.1 | 163 |
| 1989 | 50.8 | 163 |
| 1988 | 50.5 | 165 |
| 1987 | 50.3 | 168 |
| 1986 | 50.2 | 171 |