| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2014 | 56 | 17 |
| 2013 | 48 | 17 |
| 2012 | 59.4 | 15 |
| 2011 | 85.6 | 13 |
| 2010 | 70.6 | 16 |
| 2009 | 66 | 22 |
| 2008 | 163.4 | 12 |
| 2007 | 105.7 | 13 |
| 2006 | 83 | 12 |
| 2005 | 72.3 | 17 |
| 2004 | 84.9 | 14 |
| 2003 | 81.3 | 11 |
| 2002 | 106.8 | 7 |
| 2001 | 83.5 | 15 |
| 2000 | 74.7 | 16 |
| 1999 | 48.1 | 19 |
| 1998 | 399.6 | 2 |
| 1997 | 58.3 | 17 |
| 1996 | 46.1 | 15 |
| 1995 | 42.3 | 15 |
| 1994 | 45.4 | 16 |
| 1993 | 35.2 | 14 |
| 1992 | 35.7 | 13 |
| 1991 | 34.5 | 9 |
| 1990 | 39.2 | 13 |
| 1989 | 32.8 | 15 |
| 1988 | 28.9 | 13 |
| 1987 | 57.5 | 10 |
| 1986 | 36.1 | 8 |