| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 33.5 | 60 |
| 2015 | 33.1 | 62 |
| 2014 | 33 | 65 |
| 2013 | 32.7 | 68 |
| 2012 | 32.3 | 71 |
| 2011 | 32.1 | 74 |
| 2010 | 32.1 | 76 |
| 2009 | 32.1 | 77 |
| 2008 | 32.3 | 77 |
| 2007 | 32.6 | 78 |
| 2006 | 33 | 79 |
| 2005 | 33.3 | 79 |
| 2004 | 33.9 | 79 |
| 2003 | 34.5 | 80 |
| 2002 | 35.2 | 82 |
| 2001 | 35.9 | 82 |
| 2000 | 36.6 | 81 |
| 1999 | 37.2 | 80 |
| 1998 | 37.9 | 81 |
| 1997 | 38.4 | 82 |
| 1996 | 39 | 82 |
| 1995 | 39.6 | 81 |
| 1994 | 40 | 81 |
| 1993 | 40.4 | 79 |
| 1992 | 40.8 | 77 |
| 1991 | 41 | 77 |
| 1990 | 41 | 77 |
| 1989 | 41.1 | 77 |
| 1988 | 41.1 | 79 |
| 1987 | 41 | 82 |
| 1986 | 40.9 | 82 |