| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 10.7 | 93 |
| 2014 | 6.3 | 106 |
| 2013 | 6.3 | 104 |
| 2012 | 5.6 | 118 |
| 2011 | 16.4 | 77 |
| 2010 | 16.4 | 74 |
| 2009 | 8.4 | 90 |
| 2008 | 7.1 | 116 |
| 2007 | 7.1 | 108 |
| 2006 | 1.7 | 135 |
| 2005 | 1.9 | 120 |
| 2004 | 1.8 | 116 |
| 2003 | 0.8 | 126 |
| 2002 | 0.7 | 125 |
| 2001 | 0.8 | 114 |
| 2000 | 0.7 | 118 |
| 1999 | 1.2 | 102 |
| 1998 | 1.4 | 107 |
| 1997 | 1.7 | 93 |
| 1996 | 0.9 | 98 |
| 1995 | -.2 | 174 |
| 1994 | 0.7 | 85 |
| 1993 | 0.5 | 94 |
| 1992 | 0.1 | 113 |