| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2012 | 14.6 | 59 |
| 2011 | 25.6 | 59 |
| 2010 | 25.8 | 57 |
| 2009 | 27.3 | 57 |
| 2008 | 134.2 | 52 |
| 2007 | 82.5 | 54 |
| 2006 | 45.3 | 52 |
| 2005 | 164.3 | 48 |
| 2004 | 76.4 | 45 |
| 2003 | 49.1 | 45 |
| 2002 | 13.5 | 48 |
| 2001 | 41.8 | 42 |
| 2000 | 59.6 | 45 |
| 1999 | 77.8 | 41 |
| 1998 | 158.1 | 33 |
| 1997 | 257 | 29 |
| 1996 | 43.8 | 42 |
| 1995 | 45.9 | 38 |
| 1994 | 113.7 | 31 |
| 1993 | 103.4 | 27 |
| 1992 | 156.8 | 22 |
| 1991 | 48.2 | 29 |
| 1990 | 8.5 | 34 |
| 1989 | 19.2 | 29 |
| 1988 | 5.9 | 31 |