| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2012 | 42 | 51 |
| 2011 | 41.5 | 55 |
| 2010 | 52.8 | 53 |
| 2009 | 45.7 | 54 |
| 2008 | 199.5 | 48 |
| 2007 | 167.7 | 50 |
| 2006 | 35.6 | 57 |
| 2005 | 19.4 | 58 |
| 2004 | 16.7 | 52 |
| 2003 | 8.6 | 52 |
| 2002 | 4.8 | 59 |
| 2001 | 5 | 56 |
| 2000 | 2.6 | 63 |
| 1999 | 1.4 | 70 |
| 1998 | 1.6 | 69 |
| 1997 | 1.3 | 70 |
| 1996 | 0.7 | 66 |
| 1995 | 0.1 | 75 |
| 1994 | 0.2 | 71 |
| 1993 | 0.1 | 63 |
| 1992 | 0.1 | 57 |
| 1991 | 0.1 | 57 |
| 1990 | 0.1 | 49 |
| 1989 | 0 | 51 |
| 1988 | 0.1 | 48 |