| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 79.9 | 8 |
| 2015 | 68 | 10 |
| 2014 | 76.4 | 9 |
| 2013 | 83.2 | 7 |
| 2012 | 60.1 | 10 |
| 2011 | 58.1 | 12 |
| 2010 | 65.2 | 15 |
| 2009 | 44.9 | 21 |
| 2008 | 36.4 | 26 |
| 2007 | 42.9 | 30 |
| 2006 | 43.7 | 23 |
| 2005 | 47.4 | 18 |
| 2004 | 67.6 | 17 |
| 2003 | 68.7 | 10 |
| 2002 | 30.7 | 19 |
| 2001 | 25.8 | 24 |
| 2000 | 15.3 | 31 |
| 1999 | 29.5 | 26 |
| 1998 | 19.9 | 30 |
| 1997 | 11.8 | 35 |
| 1996 | 3.6 | 44 |
| 1995 | 34.8 | 8 |
| 1994 | 55.2 | 5 |
| 1993 | 67.6 | 4 |
| 1992 | 64.1 | 2 |
| 1991 | 19.7 | 10 |
| 1990 | 18.4 | 11 |
| 1989 | 17.6 | 11 |
| 1988 | 21.3 | 8 |
| 1987 | 21.4 | 10 |
| 1986 | 5.1 | 21 |