| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 28.4 | 19 |
| 2015 | 24.8 | 18 |
| 2014 | 20.5 | 25 |
| 2013 | 18.5 | 26 |
| 2012 | 23.5 | 23 |
| 2011 | 37.1 | 21 |
| 2010 | 49.5 | 18 |
| 2009 | 53.8 | 17 |
| 2008 | 58.8 | 21 |
| 2007 | 101.7 | 16 |
| 2006 | 81.9 | 15 |
| 2005 | 45.9 | 19 |
| 2004 | 34.6 | 26 |
| 2003 | 21.4 | 26 |
| 2002 | 18.7 | 24 |
| 2001 | 30.4 | 20 |
| 2000 | 35.2 | 26 |
| 1999 | 30.7 | 24 |
| 1998 | 25.8 | 25 |
| 1997 | 28.4 | 16 |
| 1996 | 21.6 | 17 |
| 1995 | 16.1 | 19 |
| 1994 | 14.3 | 22 |
| 1993 | 13.8 | 20 |
| 1992 | 7 | 21 |
| 1991 | 10.3 | 15 |
| 1990 | 12.4 | 14 |
| 1989 | 12.7 | 16 |
| 1988 | 4.7 | 22 |
| 1987 | 10.2 | 18 |
| 1986 | 2.2 | 28 |