| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 35.8 | 53 |
| 2015 | 36 | 53 |
| 2014 | 36.3 | 53 |
| 2013 | 36.6 | 53 |
| 2012 | 36.8 | 53 |
| 2011 | 36.9 | 54 |
| 2010 | 37 | 55 |
| 2009 | 37.1 | 58 |
| 2008 | 37.2 | 60 |
| 2007 | 37.4 | 61 |
| 2006 | 37.5 | 62 |
| 2005 | 37.8 | 66 |
| 2004 | 38 | 66 |
| 2003 | 38.4 | 66 |
| 2002 | 38.8 | 68 |
| 2001 | 39.1 | 68 |
| 2000 | 39.5 | 70 |
| 1999 | 39.8 | 70 |
| 1998 | 40 | 70 |
| 1997 | 40.3 | 69 |
| 1996 | 40.5 | 71 |
| 1995 | 40.7 | 72 |
| 1994 | 41.7 | 70 |
| 1993 | 42.7 | 65 |
| 1992 | 43.6 | 55 |
| 1991 | 44.6 | 48 |
| 1990 | 45.8 | 33 |
| 1989 | 46 | 30 |
| 1988 | 46.3 | 27 |
| 1987 | 46.7 | 19 |
| 1986 | 47 | 16 |