| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 0 | 182 |
| 2014 | 0 | 184 |
| 2013 | 0 | 179 |
| 2012 | 0.7 | 163 |
| 2011 | 0.4 | 171 |
| 2010 | 0.6 | 165 |
| 2009 | 0.4 | 162 |
| 2008 | 1.2 | 153 |
| 2007 | 0.6 | 171 |
| 2006 | 0.3 | 167 |
| 2005 | 0.1 | 167 |
| 2004 | 0.2 | 163 |
| 2003 | 0.1 | 165 |
| 2002 | 0.1 | 160 |
| 2001 | 0.1 | 157 |
| 2000 | 0 | 163 |
| 1999 | 0.1 | 154 |
| 1998 | 0.1 | 158 |
| 1997 | 0 | 166 |
| 1996 | 0.1 | 145 |
| 1995 | 0.1 | 146 |
| 1994 | 0 | 138 |
| 1993 | -.1 | 165 |
| 1992 | -.1 | 158 |
| 1991 | 0 | 145 |
| 1990 | 0 | 126 |
| 1989 | 0 | 116 |
| 1988 | 0 | 133 |
| 1987 | 0.1 | 87 |
| 1986 | 0.1 | 79 |