| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 5.2 | 114 |
| 2014 | 4.3 | 121 |
| 2013 | 4.5 | 115 |
| 2012 | 1.1 | 158 |
| 2011 | 1 | 155 |
| 2010 | 1.1 | 152 |
| 2009 | 1.1 | 145 |
| 2008 | 0.9 | 158 |
| 2007 | 1.4 | 146 |
| 2006 | 1 | 151 |
| 2005 | 0.2 | 160 |
| 2004 | 0 | 186 |
| 2003 | 0 | 182 |
| 2002 | 0 | 180 |
| 2001 | 0 | 170 |
| 2000 | 0 | 167 |
| 1999 | 0 | 173 |
| 1998 | 0 | 173 |
| 1997 | 0 | 168 |
| 1996 | 0 | 159 |
| 1995 | 0 | 158 |
| 1994 | 0 | 150 |
| 1993 | 0 | 147 |
| 1992 | 0 | 149 |
| 1991 | 0 | 139 |
| 1990 | 0.1 | 117 |
| 1989 | -.4 | 142 |
| 1988 | -.4 | 141 |
| 1987 | 0.6 | 52 |
| 1986 | 0 | 98 |