| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 5.2 | 111 |
| 2014 | 6 | 107 |
| 2013 | 4.5 | 112 |
| 2012 | -.1 | 191 |
| 2011 | 8.1 | 105 |
| 2010 | 1 | 155 |
| 2009 | 0.5 | 156 |
| 2008 | 2 | 140 |
| 2007 | 1.2 | 153 |
| 2006 | 0.4 | 166 |
| 2005 | 1.4 | 130 |
| 2004 | 1.1 | 126 |
| 2003 | 0.7 | 133 |
| 2002 | 0.1 | 158 |
| 2001 | 0.2 | 142 |
| 2000 | 0.3 | 139 |
| 1999 | 0.6 | 118 |
| 1998 | 0.1 | 149 |
| 1997 | 0.1 | 150 |
| 1996 | 0.2 | 140 |
| 1995 | 0.1 | 147 |
| 1994 | 0.2 | 109 |
| 1993 | 0.1 | 133 |
| 1992 | -.1 | 157 |
| 1991 | -.3 | 152 |
| 1990 | 0.2 | 87 |
| 1989 | 0.1 | 95 |
| 1988 | 0.2 | 77 |
| 1987 | 0 | 126 |
| 1986 | 0 | 123 |