| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 36.3 | 50 |
| 2015 | 36.6 | 50 |
| 2014 | 37 | 49 |
| 2013 | 37.4 | 50 |
| 2012 | 37.7 | 49 |
| 2011 | 38 | 51 |
| 2010 | 38.3 | 50 |
| 2009 | 38.5 | 49 |
| 2008 | 38.7 | 50 |
| 2007 | 38.9 | 50 |
| 2006 | 39 | 54 |
| 2005 | 39.1 | 55 |
| 2004 | 39.3 | 58 |
| 2003 | 39.4 | 61 |
| 2002 | 39.5 | 63 |
| 2001 | 39.7 | 66 |
| 2000 | 39.7 | 68 |
| 1999 | 39.9 | 69 |
| 1998 | 40.1 | 69 |
| 1997 | 40.3 | 70 |
| 1996 | 40.4 | 73 |
| 1995 | 40.6 | 73 |
| 1994 | 40.9 | 72 |
| 1993 | 41.2 | 72 |
| 1992 | 41.5 | 73 |
| 1991 | 41.7 | 72 |
| 1990 | 42 | 71 |
| 1989 | 42.3 | 71 |
| 1988 | 42.6 | 69 |
| 1987 | 42.8 | 68 |
| 1986 | 43 | 66 |