| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 3.2 | 92 |
| 2015 | 3.3 | 97 |
| 2014 | 3.3 | 100 |
| 2013 | 3 | 101 |
| 2012 | 2.7 | 101 |
| 2011 | 2.9 | 98 |
| 2010 | 2.5 | 101 |
| 2009 | 2.1 | 104 |
| 2008 | 2 | 106 |
| 2007 | 1.6 | 110 |
| 2006 | 1.6 | 103 |
| 2005 | 1.6 | 100 |
| 2004 | 1.3 | 101 |
| 2003 | 1 | 104 |
| 2002 | 0.9 | 102 |
| 2001 | 0.7 | 105 |
| 2000 | 0.5 | 106 |
| 1999 | 0.5 | 111 |
| 1998 | 0.5 | 110 |
| 1997 | 0.4 | 116 |
| 1996 | 0.4 | 113 |
| 1995 | 0.4 | 107 |
| 1994 | 0.4 | 104 |
| 1993 | 0.4 | 113 |
| 1992 | 0.4 | 103 |
| 1991 | 0.4 | 98 |
| 1990 | 0.4 | 99 |
| 1989 | 0.4 | 94 |
| 1988 | 0.4 | 93 |
| 1987 | 0.3 | 92 |
| 1986 | 0.3 | 87 |