| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 8.9 | 48 |
| 2015 | 9.5 | 100 |
| 2014 | 8.8 | 97 |
| 2013 | 8.2 | 93 |
| 2012 | 7.7 | 107 |
| 2011 | 9.4 | 101 |
| 2010 | 4.9 | 109 |
| 2009 | 4.3 | 108 |
| 2008 | 6.3 | 118 |
| 2007 | 3.8 | 123 |
| 2006 | 2.9 | 118 |
| 2005 | 2.4 | 115 |
| 2004 | 2.5 | 109 |
| 2003 | 2 | 101 |
| 2002 | 2 | 93 |
| 2001 | 1.5 | 98 |
| 2000 | 2.7 | 75 |
| 1999 | 3.4 | 75 |
| 1998 | 2.2 | 86 |
| 1997 | 2 | 87 |
| 1996 | 1.2 | 85 |
| 1995 | 0.9 | 93 |
| 1994 | 0.5 | 98 |
| 1993 | 0.4 | 97 |
| 1992 | 0.2 | 102 |
| 1991 | 0.4 | 75 |
| 1990 | 0 | 127 |
| 1989 | 0 | 113 |
| 1988 | 0 | 131 |
| 1987 | 0 | 110 |
| 1986 | 0 | 116 |