| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2012 | 49.8 | 50 |
| 2011 | 49.2 | 53 |
| 2010 | 39.7 | 54 |
| 2009 | 31.4 | 56 |
| 2008 | 51.1 | 57 |
| 2007 | 72.6 | 57 |
| 2006 | 42.8 | 54 |
| 2005 | 20.2 | 57 |
| 2004 | 11.3 | 55 |
| 2003 | 8.1 | 53 |
| 2002 | 11.3 | 50 |
| 2001 | 8.5 | 53 |
| 2000 | 15.2 | 48 |
| 1999 | 22.9 | 48 |
| 1998 | 28.3 | 46 |
| 1997 | 40.2 | 46 |
| 1996 | 38.1 | 43 |
| 1995 | 39.4 | 40 |
| 1994 | 30.8 | 41 |
| 1993 | 16.7 | 42 |
| 1992 | 4.2 | 43 |
| 1991 | 1.3 | 45 |
| 1990 | 1 | 39 |
| 1989 | 0.9 | 42 |
| 1988 | 0.6 | 40 |