| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 10.6 | 94 |
| 2014 | 4.1 | 123 |
| 2013 | 8.5 | 92 |
| 2012 | 10.8 | 94 |
| 2011 | 7.4 | 108 |
| 2010 | 7.7 | 97 |
| 2009 | 5 | 104 |
| 2008 | 7.5 | 113 |
| 2007 | 6.7 | 109 |
| 2006 | 6.1 | 98 |
| 2005 | 3.9 | 102 |
| 2004 | 2.2 | 113 |
| 2003 | 0.7 | 134 |
| 2002 | 1.5 | 103 |
| 2001 | 3.8 | 75 |
| 2000 | 2 | 84 |
| 1999 | 0 | 163 |
| 1998 | 1 | 115 |
| 1997 | 0.9 | 105 |
| 1996 | 1.3 | 83 |
| 1995 | 1.5 | 70 |
| 1994 | 1 | 80 |
| 1993 | 0.6 | 91 |
| 1992 | 1.2 | 59 |
| 1991 | 1.2 | 57 |
| 1990 | 0.3 | 85 |
| 1989 | 0 | 129 |
| 1988 | 0 | 132 |
| 1987 | 0 | 129 |
| 1986 | 0.1 | 76 |