| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 2.7 | 97 |
| 2015 | 2.2 | 107 |
| 2014 | 3.9 | 95 |
| 2013 | 7.3 | 79 |
| 2011 | 6.1 | 80 |
| 2010 | 6.2 | 80 |
| 2009 | 7.4 | 76 |
| 2008 | 6.1 | 80 |
| 2007 | 3.9 | 87 |
| 2006 | 2.2 | 94 |
| 2005 | 0.6 | 126 |
| 2004 | 0.5 | 126 |
| 2003 | 0.4 | 127 |
| 2002 | 0.3 | 122 |
| 2001 | 0.3 | 123 |
| 2000 | 0.2 | 128 |
| 1999 | 0.2 | 128 |
| 1998 | 0.2 | 129 |
| 1997 | 0.2 | 134 |
| 1996 | 0.2 | 125 |
| 1995 | 0.2 | 124 |
| 1994 | 0.2 | 123 |
| 1993 | 0.4 | 111 |
| 1992 | 0.4 | 104 |
| 1990 | 0.3 | 102 |
| 1989 | 0.6 | 87 |
| 1988 | 0.8 | 84 |
| 1987 | 0.3 | 93 |
| 1986 | 0.5 | 79 |