| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 66 | 76 |
| 2015 | 65.5 | 92 |
| 2014 | 65 | 103 |
| 2013 | 64.6 | 107 |
| 2012 | 64.1 | 111 |
| 2011 | 63.7 | 115 |
| 2010 | 63.2 | 116 |
| 2009 | 62.8 | 118 |
| 2008 | 62.4 | 118 |
| 2007 | 62 | 119 |
| 2006 | 61.6 | 119 |
| 2005 | 61.3 | 118 |
| 2004 | 60.8 | 118 |
| 2003 | 60.4 | 118 |
| 2002 | 59.9 | 115 |
| 2001 | 59.5 | 116 |
| 2000 | 59.1 | 115 |
| 1999 | 58.6 | 115 |
| 1998 | 58.1 | 112 |
| 1997 | 57.6 | 113 |
| 1996 | 57.2 | 114 |
| 1995 | 56.7 | 113 |
| 1994 | 56.2 | 114 |
| 1993 | 55.7 | 116 |
| 1992 | 55.3 | 118 |
| 1991 | 54.9 | 120 |
| 1990 | 54.5 | 121 |
| 1989 | 54.1 | 122 |
| 1988 | 53.8 | 124 |
| 1987 | 53.6 | 124 |
| 1986 | 53.4 | 127 |