| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 72.3 | 12 |
| 2015 | 72.2 | 13 |
| 2014 | 72 | 13 |
| 2013 | 71.7 | 13 |
| 2012 | 71.5 | 16 |
| 2011 | 71.1 | 17 |
| 2010 | 70.6 | 21 |
| 2009 | 70.3 | 22 |
| 2008 | 70 | 21 |
| 2007 | 69.7 | 23 |
| 2006 | 69.4 | 24 |
| 2005 | 69.2 | 24 |
| 2004 | 68.8 | 28 |
| 2003 | 68.3 | 33 |
| 2002 | 67.9 | 36 |
| 2001 | 67.4 | 43 |
| 2000 | 67 | 49 |
| 1999 | 66.3 | 53 |
| 1998 | 65.7 | 56 |
| 1997 | 65.1 | 58 |
| 1996 | 64.6 | 61 |
| 1995 | 64.2 | 67 |
| 1994 | 63.8 | 68 |
| 1993 | 63.5 | 70 |
| 1992 | 63.2 | 69 |
| 1991 | 63 | 69 |
| 1990 | 62.7 | 69 |
| 1989 | 62.2 | 72 |
| 1988 | 61.5 | 73 |
| 1987 | 60.8 | 75 |
| 1986 | 59.9 | 79 |