| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 33.2 | 15 |
| 2015 | 37.6 | 16 |
| 2014 | 42.2 | 17 |
| 2013 | 44 | 16 |
| 2012 | 39.3 | 18 |
| 2011 | 43.7 | 16 |
| 2010 | 45 | 20 |
| 2009 | 40 | 25 |
| 2008 | 35.7 | 27 |
| 2007 | 79.9 | 22 |
| 2006 | 42.5 | 24 |
| 2005 | 31.1 | 23 |
| 2004 | 43.4 | 22 |
| 2003 | 41.5 | 20 |
| 2002 | 25.5 | 21 |
| 2001 | 22.7 | 25 |
| 2000 | 56 | 19 |
| 1999 | 53.1 | 16 |
| 1998 | 36.8 | 20 |
| 1997 | 42.6 | 11 |
| 1996 | 25.4 | 14 |
| 1995 | 67.8 | 3 |
| 1994 | 16 | 19 |
| 1993 | 21.2 | 13 |
| 1992 | 31.4 | 6 |
| 1991 | 21.7 | 9 |
| 1990 | 24.3 | 10 |
| 1989 | 17 | 12 |
| 1988 | 7.1 | 14 |
| 1987 | 11.8 | 16 |
| 1986 | 4.2 | 22 |