| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2014 | 41 | 18 |
| 2013 | 39.4 | 18 |
| 2012 | 40.1 | 17 |
| 2011 | 46.5 | 15 |
| 2010 | 51 | 17 |
| 2009 | 47.7 | 20 |
| 2008 | 82.3 | 15 |
| 2007 | 108.7 | 14 |
| 2006 | 86.7 | 14 |
| 2005 | 57.7 | 15 |
| 2004 | 62.3 | 18 |
| 2003 | 59.7 | 15 |
| 2002 | 68.8 | 9 |
| 2001 | 71 | 10 |
| 2000 | 78.9 | 15 |
| 1999 | 48.2 | 18 |
| 1998 | 40 | 15 |
| 1997 | 26.9 | 19 |
| 1996 | 16.7 | 21 |
| 1995 | 13.1 | 23 |
| 1994 | 14.7 | 20 |
| 1993 | 12.1 | 23 |
| 1992 | 8.3 | 19 |
| 1991 | 9.7 | 17 |
| 1990 | 9.6 | 17 |
| 1989 | 10.8 | 18 |
| 1988 | 6.3 | 18 |
| 1987 | 9.5 | 19 |
| 1986 | 7.1 | 14 |