| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 33.3 | 62 |
| 2015 | 33.7 | 61 |
| 2014 | 34.1 | 61 |
| 2013 | 34.6 | 61 |
| 2012 | 35.1 | 62 |
| 2011 | 35.7 | 62 |
| 2010 | 36.3 | 60 |
| 2009 | 37 | 60 |
| 2008 | 37.8 | 55 |
| 2007 | 38.6 | 53 |
| 2006 | 39.4 | 48 |
| 2005 | 40.3 | 47 |
| 2004 | 41 | 46 |
| 2003 | 41.7 | 44 |
| 2002 | 42.3 | 44 |
| 2001 | 42.8 | 41 |
| 2000 | 43.4 | 39 |
| 1999 | 43.8 | 37 |
| 1998 | 44.1 | 37 |
| 1997 | 44.4 | 38 |
| 1996 | 44.5 | 36 |
| 1995 | 44.5 | 38 |
| 1994 | 44.6 | 37 |
| 1993 | 44.6 | 42 |
| 1992 | 44.5 | 48 |
| 1991 | 44.4 | 50 |
| 1990 | 44.3 | 51 |
| 1989 | 44.3 | 51 |
| 1988 | 44.4 | 52 |
| 1987 | 44.4 | 54 |
| 1986 | 44.5 | 56 |