| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 0.4 | 169 |
| 2014 | 0.2 | 177 |
| 2013 | 0.1 | 175 |
| 2012 | 0.1 | 182 |
| 2011 | 0.1 | 178 |
| 2010 | 0 | 187 |
| 2009 | 0.1 | 175 |
| 2008 | 0.5 | 170 |
| 2007 | 0.1 | 186 |
| 2006 | 0.2 | 173 |
| 2005 | 0 | 174 |
| 2004 | 0 | 175 |
| 2003 | 0 | 177 |
| 2002 | 0 | 174 |
| 2001 | 0 | 166 |
| 2000 | 0 | 173 |
| 1999 | 0 | 161 |
| 1998 | 0 | 166 |
| 1997 | 0.2 | 142 |
| 1996 | 0 | 160 |
| 1995 | 0 | 149 |
| 1994 | 0 | 140 |
| 1993 | 0.1 | 139 |
| 1992 | 0.1 | 125 |
| 1991 | 0 | 119 |
| 1990 | 0.1 | 111 |
| 1989 | 0 | 127 |
| 1988 | 0 | 128 |
| 1987 | 0 | 120 |
| 1986 | 0 | 120 |