| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 35.2 | 56 |
| 2015 | 35.1 | 56 |
| 2014 | 35.1 | 57 |
| 2013 | 35.2 | 58 |
| 2012 | 35.4 | 59 |
| 2011 | 35.6 | 63 |
| 2010 | 35.7 | 64 |
| 2009 | 36.1 | 65 |
| 2008 | 36.5 | 64 |
| 2007 | 36.8 | 64 |
| 2006 | 37.4 | 64 |
| 2005 | 38.1 | 62 |
| 2004 | 38.9 | 61 |
| 2003 | 39.8 | 57 |
| 2002 | 40.8 | 50 |
| 2001 | 41.8 | 48 |
| 2000 | 42.5 | 45 |
| 1999 | 43.1 | 45 |
| 1998 | 43.5 | 45 |
| 1997 | 43.8 | 44 |
| 1996 | 44 | 44 |
| 1995 | 44.3 | 41 |
| 1994 | 44.3 | 45 |
| 1993 | 44.4 | 45 |
| 1992 | 44.3 | 51 |
| 1991 | 44.1 | 53 |
| 1990 | 43.8 | 59 |
| 1989 | 43.7 | 61 |
| 1988 | 43.6 | 61 |
| 1987 | 43.4 | 64 |
| 1986 | 43.1 | 65 |