| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 37.4 | 46 |
| 2015 | 37.4 | 46 |
| 2014 | 37.6 | 46 |
| 2013 | 37.8 | 45 |
| 2012 | 38.1 | 45 |
| 2011 | 38.3 | 47 |
| 2010 | 38.4 | 47 |
| 2009 | 38.6 | 48 |
| 2008 | 38.8 | 48 |
| 2007 | 39 | 48 |
| 2006 | 39.3 | 50 |
| 2005 | 39.5 | 53 |
| 2004 | 39.7 | 54 |
| 2003 | 39.8 | 56 |
| 2002 | 40.1 | 59 |
| 2001 | 40.4 | 60 |
| 2000 | 40.6 | 63 |
| 1999 | 41 | 63 |
| 1998 | 41.4 | 60 |
| 1997 | 41.9 | 60 |
| 1996 | 42.4 | 59 |
| 1995 | 42.7 | 56 |
| 1994 | 42.9 | 57 |
| 1993 | 43 | 58 |
| 1992 | 43 | 67 |
| 1991 | 43 | 67 |
| 1990 | 43 | 68 |
| 1989 | 42.7 | 68 |
| 1988 | 42.4 | 70 |
| 1987 | 42.1 | 72 |
| 1986 | 41.6 | 78 |