| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 3.1 | 128 |
| 2014 | 3.5 | 133 |
| 2013 | 2.6 | 133 |
| 2012 | 3.8 | 130 |
| 2011 | 4 | 129 |
| 2010 | 3.6 | 120 |
| 2009 | 1.6 | 129 |
| 2008 | 3.4 | 131 |
| 2007 | 3.8 | 124 |
| 2006 | 4.6 | 105 |
| 2005 | 1.8 | 123 |
| 2004 | 2.5 | 108 |
| 2003 | 0.4 | 145 |
| 2002 | 0.3 | 140 |
| 2001 | 0.4 | 131 |
| 2000 | 0 | 166 |
| 1999 | -.3 | 178 |
| 1998 | 1.1 | 111 |
| 1997 | 0.2 | 149 |
| 1996 | 0 | 155 |
| 1995 | 0.7 | 99 |
| 1994 | 0.7 | 87 |
| 1993 | 0.9 | 78 |
| 1992 | 1 | 65 |
| 1991 | 0.1 | 115 |
| 1990 | 0.9 | 59 |
| 1989 | 0.1 | 98 |
| 1988 | 0.3 | 68 |
| 1987 | 0.2 | 78 |
| 1986 | 0.1 | 80 |