| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 31.2 | 18 |
| 2015 | 23.3 | 19 |
| 2014 | 26.2 | 24 |
| 2013 | 29.9 | 21 |
| 2012 | 33.7 | 21 |
| 2011 | 31.5 | 23 |
| 2010 | 41.1 | 22 |
| 2009 | 42.5 | 22 |
| 2008 | 33.6 | 28 |
| 2007 | 46.2 | 29 |
| 2006 | 25.2 | 33 |
| 2005 | 19.2 | 31 |
| 2004 | 17 | 33 |
| 2003 | 12.6 | 33 |
| 2002 | 7.8 | 33 |
| 2001 | 11.5 | 33 |
| 2000 | 14.3 | 33 |
| 1999 | 26.5 | 28 |
| 1998 | 20 | 29 |
| 1997 | 24.6 | 22 |
| 1996 | 13.7 | 26 |
| 1995 | 10 | 29 |
| 1994 | 14.6 | 21 |
| 1993 | 8 | 29 |
| 1992 | 5.8 | 24 |
| 1991 | 2 | 30 |
| 1990 | 1.3 | 31 |
| 1989 | 1 | 31 |
| 1988 | 1.8 | 30 |
| 1987 | 3.3 | 27 |
| 1986 | 10.8 | 12 |