| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 9.1 | 131 |
| 2014 | 9 | 132 |
| 2013 | 9 | 134 |
| 2012 | 9.1 | 134 |
| 2011 | 8.9 | 131 |
| 2010 | 8.7 | 142 |
| 2009 | 8.8 | 130 |
| 2008 | 8.7 | 126 |
| 2007 | 8.5 | 126 |
| 2006 | 8.4 | 121 |
| 2005 | 8.3 | 119 |
| 2004 | 8.5 | 116 |
| 2003 | 8.1 | 116 |
| 2002 | 8 | 114 |
| 2001 | 8 | 112 |
| 2000 | 8.1 | 109 |
| 1999 | 7.7 | 107 |
| 1998 | 7.4 | 108 |
| 1997 | 7.1 | 105 |
| 1996 | 7.4 | 104 |
| 1995 | 6.9 | 103 |
| 1994 | 8 | 96 |
| 1993 | 10.9 | 89 |
| 1992 | 13.6 | 82 |
| 1991 | 16.4 | 74 |
| 1990 | 19.2 | 67 |