| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 36.9 | 47 |
| 2015 | 37 | 48 |
| 2014 | 37.3 | 48 |
| 2013 | 37.5 | 48 |
| 2012 | 37.7 | 48 |
| 2011 | 38 | 50 |
| 2010 | 38.4 | 48 |
| 2009 | 38.7 | 47 |
| 2008 | 39 | 47 |
| 2007 | 39.3 | 47 |
| 2006 | 39.6 | 47 |
| 2005 | 39.8 | 49 |
| 2004 | 40.1 | 49 |
| 2003 | 40.2 | 51 |
| 2002 | 40.4 | 54 |
| 2001 | 40.4 | 58 |
| 2000 | 40.5 | 64 |
| 1999 | 40.9 | 64 |
| 1998 | 41.2 | 65 |
| 1997 | 41.5 | 64 |
| 1996 | 41.8 | 64 |
| 1995 | 42 | 65 |
| 1994 | 42.4 | 64 |
| 1993 | 42.7 | 64 |
| 1992 | 43.1 | 65 |
| 1991 | 43.4 | 62 |
| 1990 | 43.7 | 61 |
| 1989 | 44.3 | 50 |
| 1988 | 45 | 47 |
| 1987 | 45.7 | 40 |
| 1986 | 46.4 | 27 |