| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 67.7 | 50 |
| 2015 | 67.7 | 52 |
| 2014 | 67.7 | 56 |
| 2013 | 67.4 | 60 |
| 2012 | 67.1 | 67 |
| 2011 | 66.7 | 79 |
| 2010 | 66.4 | 82 |
| 2009 | 65.7 | 92 |
| 2008 | 65 | 99 |
| 2007 | 64.3 | 103 |
| 2006 | 63.4 | 106 |
| 2005 | 62.6 | 109 |
| 2004 | 61.6 | 112 |
| 2003 | 60.7 | 115 |
| 2002 | 59.8 | 117 |
| 2001 | 59 | 118 |
| 2000 | 58.1 | 119 |
| 1999 | 57.4 | 120 |
| 1998 | 56.7 | 122 |
| 1997 | 56.1 | 122 |
| 1996 | 55.7 | 122 |
| 1995 | 55.3 | 124 |
| 1994 | 55.1 | 124 |
| 1993 | 55 | 121 |
| 1992 | 55 | 119 |
| 1991 | 55.1 | 118 |
| 1990 | 55.2 | 116 |
| 1989 | 55.2 | 114 |
| 1988 | 55.2 | 113 |
| 1987 | 55.1 | 112 |
| 1986 | 55.1 | 110 |