| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 66.4 | 70 |
| 2015 | 66.4 | 74 |
| 2014 | 66.3 | 80 |
| 2013 | 66.1 | 85 |
| 2012 | 65.8 | 93 |
| 2011 | 65.5 | 96 |
| 2010 | 65.2 | 100 |
| 2009 | 64.8 | 102 |
| 2008 | 64.3 | 105 |
| 2007 | 63.8 | 106 |
| 2006 | 63.2 | 107 |
| 2005 | 62.3 | 112 |
| 2004 | 61.4 | 115 |
| 2003 | 60.3 | 119 |
| 2002 | 59.1 | 120 |
| 2001 | 58.1 | 120 |
| 2000 | 57.2 | 123 |
| 1999 | 56.4 | 124 |
| 1998 | 55.7 | 126 |
| 1997 | 55.1 | 128 |
| 1996 | 54.6 | 131 |
| 1995 | 54 | 136 |
| 1994 | 53.4 | 135 |
| 1993 | 53.1 | 135 |
| 1992 | 52.9 | 134 |
| 1991 | 53 | 131 |
| 1990 | 53.2 | 128 |
| 1989 | 54 | 124 |
| 1988 | 54.6 | 117 |
| 1987 | 54.9 | 113 |
| 1986 | 55.3 | 107 |