| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 17 | 72 |
| 2014 | 17.3 | 77 |
| 2013 | 13.5 | 77 |
| 2012 | 14.4 | 85 |
| 2011 | 8 | 106 |
| 2010 | 7.4 | 99 |
| 2009 | 5.1 | 103 |
| 2008 | 8.2 | 109 |
| 2007 | 8.7 | 97 |
| 2006 | 4.8 | 101 |
| 2005 | 3.8 | 104 |
| 2004 | 1.3 | 122 |
| 2003 | 0.8 | 128 |
| 2002 | 1.3 | 107 |
| 2001 | 1.5 | 99 |
| 2000 | 1.2 | 106 |
| 1999 | 2.3 | 86 |
| 1998 | 2.4 | 84 |
| 1997 | 2 | 86 |
| 1996 | 2.9 | 64 |
| 1995 | 1.5 | 71 |
| 1994 | 0.7 | 86 |
| 1993 | 0.5 | 93 |
| 1992 | 0.3 | 84 |