| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 1.1 | 153 |
| 2014 | 1 | 152 |
| 2013 | 1.6 | 141 |
| 2012 | 1.6 | 151 |
| 2011 | 1.2 | 151 |
| 2010 | 1.8 | 140 |
| 2009 | 0.6 | 154 |
| 2008 | 0.3 | 175 |
| 2007 | 0.7 | 165 |
| 2006 | 1.6 | 136 |
| 2005 | 0.3 | 159 |
| 2004 | 0.1 | 170 |
| 2003 | 0.1 | 161 |
| 2002 | 0.1 | 159 |
| 2001 | 0 | 160 |
| 2000 | 0.1 | 151 |
| 1999 | 0.3 | 140 |
| 1998 | 0.1 | 153 |
| 1997 | 0 | 160 |
| 1996 | 0 | 153 |
| 1995 | 0.1 | 139 |
| 1994 | 0 | 166 |
| 1993 | 0 | 162 |
| 1992 | 0 | 154 |
| 1991 | 0 | 143 |
| 1990 | 0.1 | 106 |
| 1989 | 0.1 | 94 |
| 1988 | 0.1 | 93 |
| 1987 | 0 | 103 |
| 1986 | 0 | 91 |