| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 11 | 126 |
| 2014 | 10 | 129 |
| 2013 | 9.4 | 133 |
| 2012 | 8.9 | 135 |
| 2011 | 8.7 | 134 |
| 2010 | 9.3 | 136 |
| 2009 | 9.2 | 127 |
| 2008 | 8.1 | 130 |
| 2007 | 7.6 | 128 |
| 2006 | 7.2 | 126 |
| 2005 | 6.7 | 123 |
| 2004 | 6.5 | 122 |
| 2003 | 5.3 | 126 |
| 2002 | 4.4 | 128 |
| 2001 | 4.6 | 123 |
| 2000 | 4.5 | 121 |
| 1999 | 5.5 | 114 |
| 1998 | 4.4 | 117 |
| 1997 | 4.3 | 116 |
| 1996 | 4.5 | 113 |
| 1995 | 3.7 | 114 |
| 1994 | 3.8 | 108 |
| 1993 | 3.6 | 104 |
| 1992 | 3.3 | 101 |
| 1991 | 2.6 | 102 |
| 1990 | 2.4 | 100 |
| 1989 | 2 | 87 |
| 1988 | 1.9 | 85 |
| 1987 | 1.9 | 86 |
| 1986 | 2 | 85 |