| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 33.3 | 43 |
| 2015 | 32.7 | 47 |
| 2014 | 40.5 | 45 |
| 2013 | 40.7 | 47 |
| 2012 | 34 | 48 |
| 2011 | 33.4 | 48 |
| 2010 | 31.6 | 49 |
| 2009 | 30.6 | 49 |
| 2008 | 29.4 | 50 |
| 2007 | 24.1 | 49 |
| 2006 | 21.3 | 48 |
| 2005 | 20.3 | 46 |
| 2004 | 19.4 | 44 |
| 2003 | 18.2 | 45 |
| 2002 | 14.7 | 44 |
| 2001 | 14.7 | 45 |
| 2000 | 8.6 | 54 |
| 1999 | 12.1 | 46 |
| 1998 | 14.4 | 44 |
| 1997 | 14 | 49 |
| 1996 | 14.5 | 47 |
| 1995 | 14.4 | 45 |
| 1994 | 13.7 | 44 |
| 1993 | 12.5 | 44 |
| 1992 | 12.3 | 41 |
| 1991 | 11.5 | 42 |
| 1990 | 10.7 | 43 |
| 1989 | 9.9 | 43 |
| 1988 | 9.2 | 47 |
| 1987 | 8.2 | 46 |
| 1986 | 7.3 | 42 |