| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2012 | 125.5 | 45 |
| 2011 | 181.6 | 45 |
| 2010 | 146.9 | 48 |
| 2009 | 146 | 50 |
| 2008 | 92.4 | 54 |
| 2007 | 48 | 61 |
| 2006 | 9.4 | 73 |
| 2005 | 10 | 62 |
| 2004 | 8.9 | 58 |
| 2003 | 3.3 | 63 |
| 2002 | 6.7 | 54 |
| 2001 | 7.4 | 55 |
| 2000 | 7.7 | 53 |
| 1999 | 7.9 | 51 |
| 1998 | 7.9 | 55 |
| 1997 | 3.9 | 58 |
| 1996 | 7.2 | 51 |
| 1995 | 1.6 | 61 |
| 1994 | 1.1 | 60 |
| 1993 | 0.2 | 60 |
| 1992 | 0.1 | 59 |
| 1991 | 0 | 61 |
| 1990 | 0.1 | 53 |
| 1989 | 0.1 | 50 |
| 1988 | 0 | 50 |