| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2012 | 1.2 | 80 |
| 2011 | 1.6 | 78 |
| 2010 | 1.4 | 81 |
| 2009 | 2.3 | 79 |
| 2008 | 3.5 | 78 |
| 2007 | 3.5 | 79 |
| 2006 | 4.2 | 77 |
| 2005 | 6.3 | 70 |
| 2004 | 5.3 | 62 |
| 2003 | 4 | 62 |
| 2002 | 1.7 | 70 |
| 2001 | 1.7 | 68 |
| 2000 | 1.4 | 75 |
| 1999 | 0.9 | 72 |
| 1998 | 1.8 | 68 |
| 1997 | 1.3 | 69 |
| 1996 | 1.1 | 63 |
| 1995 | 1.4 | 63 |
| 1994 | 0.5 | 67 |
| 1993 | 0.6 | 53 |
| 1992 | 0.2 | 54 |
| 1991 | 0.8 | 49 |
| 1990 | 0.6 | 43 |
| 1989 | 0.4 | 45 |
| 1988 | 0.2 | 44 |