| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 10.8 | 91 |
| 2014 | 9.1 | 95 |
| 2013 | 4.3 | 117 |
| 2012 | 2.9 | 136 |
| 2011 | 3 | 135 |
| 2010 | 2.8 | 127 |
| 2009 | 3.2 | 117 |
| 2008 | 2.3 | 136 |
| 2007 | 3.2 | 131 |
| 2006 | 1.9 | 133 |
| 2005 | 0.3 | 157 |
| 2004 | 0.2 | 162 |
| 2003 | 0.2 | 155 |
| 2002 | 0 | 165 |
| 2001 | 0.2 | 136 |
| 2000 | 0.3 | 134 |
| 1999 | 0.5 | 127 |
| 1998 | 0.5 | 129 |
| 1997 | 0.9 | 106 |
| 1996 | 1.6 | 77 |
| 1995 | 1 | 89 |
| 1994 | 0.6 | 93 |
| 1993 | 0.3 | 102 |
| 1992 | 0.1 | 116 |
| 1991 | 0.1 | 112 |
| 1990 | 0.1 | 112 |
| 1989 | 0 | 107 |
| 1988 | 0 | 109 |