| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 0.1 | 69 |
| 2015 | 0.1 | 179 |
| 2014 | 0.3 | 172 |
| 2013 | 0.2 | 169 |
| 2012 | 0.2 | 176 |
| 2011 | 0.3 | 174 |
| 2010 | 0.8 | 162 |
| 2009 | 0.2 | 169 |
| 2008 | 0 | 186 |
| 2007 | 0.7 | 166 |
| 2006 | 0.1 | 180 |
| 2005 | 0.1 | 172 |
| 2004 | 0.1 | 165 |
| 2003 | 0 | 176 |
| 2002 | 0 | 172 |
| 1999 | 0 | 164 |
| 1997 | 0 | 176 |
| 1996 | 0 | 158 |
| 1995 | 0 | 163 |
| 1994 | 0 | 160 |
| 1993 | 0 | 156 |
| 1992 | 0 | 147 |
| 1991 | 0 | 133 |
| 1990 | 0 | 123 |