| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 38.4 | 21 |
| 2015 | 31.8 | 22 |
| 2014 | 26.3 | 34 |
| 2013 | 24.6 | 32 |
| 2012 | 25 | 30 |
| 2011 | 28.6 | 34 |
| 2010 | 30 | 33 |
| 2009 | 27.2 | 38 |
| 2008 | 42 | 39 |
| 2007 | 31.1 | 38 |
| 2006 | 24.4 | 36 |
| 2005 | 20.3 | 36 |
| 2004 | 18.9 | 39 |
| 2003 | 18.8 | 38 |
| 2002 | 26.2 | 29 |
| 2001 | 24 | 36 |
| 2000 | 34.5 | 32 |
| 1999 | 28 | 35 |
| 1998 | 32.2 | 35 |
| 1997 | 18.3 | 42 |
| 1996 | 11 | 36 |
| 1995 | 5.7 | 43 |
| 1994 | 5.1 | 41 |
| 1993 | 3.6 | 36 |
| 1992 | 4.4 | 27 |
| 1991 | 4.4 | 27 |
| 1990 | 6 | 26 |
| 1989 | 5.1 | 26 |
| 1988 | 3.5 | 25 |
| 1987 | 7.1 | 25 |
| 1986 | 5.1 | 25 |