| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 2.6 | 133 |
| 2014 | 0.5 | 161 |
| 2013 | 1.8 | 140 |
| 2012 | 1.2 | 155 |
| 2011 | 7.3 | 110 |
| 2010 | 1.2 | 147 |
| 2009 | 0.5 | 160 |
| 2008 | 0.5 | 167 |
| 2007 | 0.6 | 169 |
| 2006 | 0.9 | 152 |
| 2005 | 1 | 135 |
| 2004 | 0.8 | 133 |
| 2003 | 0.5 | 142 |
| 2002 | 0.6 | 128 |
| 2001 | 0.7 | 118 |
| 2000 | 0.5 | 126 |
| 1999 | 0.4 | 131 |
| 1998 | 0.3 | 136 |
| 1997 | 0.2 | 141 |
| 1996 | 0.2 | 135 |
| 1995 | 0.3 | 119 |
| 1994 | 0.2 | 123 |
| 1993 | -.1 | 166 |
| 1992 | -.1 | 161 |
| 1991 | 0.1 | 114 |
| 1990 | 0.2 | 92 |
| 1989 | 0.1 | 96 |
| 1988 | 0.1 | 88 |
| 1987 | 0.1 | 94 |
| 1986 | 0.1 | 85 |