| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 69.1 | 35 |
| 2015 | 68.9 | 40 |
| 2014 | 68.5 | 45 |
| 2013 | 68.1 | 52 |
| 2012 | 67.6 | 58 |
| 2011 | 67.2 | 68 |
| 2010 | 66.7 | 77 |
| 2009 | 66.3 | 81 |
| 2008 | 65.9 | 87 |
| 2007 | 65.5 | 91 |
| 2006 | 65.2 | 92 |
| 2005 | 64.8 | 91 |
| 2004 | 64.8 | 86 |
| 2003 | 64.7 | 83 |
| 2002 | 64.4 | 81 |
| 2001 | 64.1 | 79 |
| 2000 | 63.9 | 78 |
| 1999 | 63.7 | 77 |
| 1998 | 63.5 | 75 |
| 1997 | 63.1 | 75 |
| 1996 | 62.6 | 75 |
| 1995 | 61.9 | 79 |
| 1994 | 61.7 | 78 |
| 1993 | 61.6 | 76 |
| 1992 | 61.6 | 74 |
| 1991 | 61.5 | 76 |
| 1990 | 61.3 | 77 |
| 1989 | 62.3 | 70 |
| 1988 | 62.9 | 63 |
| 1987 | 63 | 62 |
| 1986 | 62.9 | 63 |