| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2012 | 10.1 | 63 |
| 2011 | 8.8 | 64 |
| 2010 | 10.8 | 64 |
| 2009 | 5 | 70 |
| 2008 | 14.4 | 67 |
| 2007 | 13.2 | 68 |
| 2006 | 13 | 65 |
| 2005 | 5 | 71 |
| 2004 | 3.4 | 72 |
| 2003 | 2.1 | 70 |
| 2002 | 0.4 | 85 |
| 2001 | 0.4 | 85 |
| 2000 | 0.5 | 84 |
| 1999 | 0.7 | 77 |
| 1998 | 0.8 | 79 |
| 1997 | 1.1 | 71 |
| 1996 | 0.7 | 68 |
| 1995 | 0.7 | 65 |
| 1994 | 0.6 | 66 |
| 1993 | 0.1 | 61 |
| 1992 | 0.1 | 58 |
| 1991 | 0.1 | 55 |
| 1990 | 0.1 | 50 |