| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 0.9 | 158 |
| 2014 | 0.7 | 157 |
| 2013 | 1.4 | 142 |
| 2012 | 6.1 | 113 |
| 2011 | 9.6 | 97 |
| 2010 | 1 | 153 |
| 2009 | 1.4 | 132 |
| 2008 | 3.8 | 126 |
| 2007 | 3.9 | 122 |
| 2006 | 1.3 | 141 |
| 2005 | 1.1 | 133 |
| 2004 | 0 | 180 |
| 2003 | 0.8 | 129 |
| 2002 | 0 | 182 |
| 2001 | 0 | 165 |
| 2000 | 0.1 | 154 |
| 1999 | 0.6 | 115 |
| 1998 | 0.2 | 144 |
| 1997 | 0.2 | 147 |
| 1996 | 0.2 | 124 |
| 1995 | 0 | 160 |
| 1994 | 0 | 153 |
| 1993 | 0 | 145 |
| 1992 | 0.2 | 97 |
| 1991 | 0.4 | 78 |
| 1990 | 0.2 | 93 |
| 1989 | 0.1 | 88 |
| 1988 | 0.2 | 81 |
| 1987 | 0.1 | 85 |
| 1986 | 0.1 | 78 |