| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 36.1 | 51 |
| 2015 | 36.5 | 51 |
| 2014 | 36.8 | 52 |
| 2013 | 37.2 | 51 |
| 2012 | 37.7 | 50 |
| 2011 | 38.1 | 49 |
| 2010 | 38.2 | 51 |
| 2009 | 38.4 | 51 |
| 2008 | 38.5 | 51 |
| 2007 | 38.7 | 52 |
| 2006 | 39.1 | 53 |
| 2005 | 39.7 | 50 |
| 2004 | 40 | 51 |
| 2003 | 40.3 | 49 |
| 2002 | 40.7 | 51 |
| 2001 | 41.1 | 51 |
| 2000 | 41.5 | 52 |
| 1999 | 41.7 | 53 |
| 1998 | 42 | 55 |
| 1997 | 42.2 | 56 |
| 1996 | 42.5 | 56 |
| 1995 | 42.7 | 54 |
| 1994 | 43 | 56 |
| 1993 | 43.2 | 56 |
| 1992 | 43.4 | 57 |
| 1991 | 43.6 | 60 |
| 1990 | 43.8 | 57 |
| 1989 | 43.8 | 59 |
| 1988 | 43.9 | 60 |
| 1987 | 43.9 | 59 |
| 1986 | 44.1 | 60 |