| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 0.1 | 181 |
| 2014 | 0 | 183 |
| 2013 | 0 | 178 |
| 2012 | 0.1 | 184 |
| 2011 | 0.2 | 176 |
| 2010 | 0.1 | 182 |
| 2009 | 0.1 | 174 |
| 2008 | 0 | 184 |
| 2007 | 0.1 | 183 |
| 2006 | 0 | 182 |
| 2005 | 0 | 181 |
| 2004 | 0 | 178 |
| 2003 | 0 | 178 |
| 2002 | 0 | 177 |
| 2001 | 0 | 167 |
| 2000 | 0 | 169 |
| 1999 | 0 | 170 |
| 1998 | 0 | 169 |
| 1997 | 0 | 171 |
| 1996 | 0 | 165 |
| 1995 | 0 | 159 |
| 1994 | 0 | 154 |
| 1993 | 0 | 154 |
| 1992 | 0 | 152 |
| 1991 | 0 | 121 |
| 1990 | 0 | 131 |
| 1989 | 0 | 112 |
| 1988 | 0 | 103 |
| 1987 | 0.1 | 93 |