| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 37.4 | 44 |
| 2015 | 37.6 | 45 |
| 2014 | 37.9 | 44 |
| 2013 | 38.3 | 44 |
| 2012 | 38.7 | 44 |
| 2011 | 39.1 | 45 |
| 2010 | 39.5 | 45 |
| 2009 | 40 | 45 |
| 2008 | 40.5 | 45 |
| 2007 | 41 | 45 |
| 2006 | 41.6 | 42 |
| 2005 | 42.1 | 38 |
| 2004 | 42.5 | 37 |
| 2003 | 43 | 34 |
| 2002 | 43.5 | 34 |
| 2001 | 44 | 31 |
| 2000 | 44.5 | 30 |
| 1999 | 45.2 | 26 |
| 1998 | 45.8 | 18 |
| 1997 | 46.3 | 16 |
| 1996 | 46.8 | 11 |
| 1995 | 47.2 | 10 |
| 1994 | 47.5 | 9 |
| 1993 | 47.8 | 9 |
| 1992 | 47.9 | 9 |
| 1991 | 47.9 | 10 |
| 1990 | 47.9 | 9 |
| 1989 | 48.2 | 6 |
| 1988 | 48.4 | 5 |
| 1987 | 48.6 | 4 |
| 1986 | 48.7 | 4 |