| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 3.5 | 123 |
| 2014 | 4 | 127 |
| 2013 | 3.1 | 128 |
| 2012 | 2.8 | 141 |
| 2011 | 3.4 | 133 |
| 2010 | 2.7 | 128 |
| 2009 | 3.3 | 115 |
| 2008 | 4.5 | 125 |
| 2007 | 3.5 | 128 |
| 2006 | 2.9 | 117 |
| 2005 | 1.7 | 126 |
| 2004 | 1.4 | 121 |
| 2003 | 0.9 | 125 |
| 2002 | 0.8 | 117 |
| 2001 | 0.5 | 128 |
| 2000 | 0.8 | 117 |
| 1999 | 1.5 | 97 |
| 1998 | 0.7 | 122 |
| 1997 | 1.8 | 90 |
| 1996 | 0.1 | 150 |
| 1995 | 0.3 | 114 |
| 1994 | 0.7 | 88 |
| 1993 | 0 | 161 |
| 1992 | 0.2 | 93 |
| 1991 | -.1 | 147 |
| 1990 | 0.6 | 67 |
| 1989 | 0.3 | 71 |
| 1988 | 0.1 | 84 |
| 1987 | 0 | 133 |
| 1986 | -.1 | 128 |