| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 6.4 | 52 |
| 2015 | 13.2 | 83 |
| 2014 | 7.7 | 100 |
| 2013 | 7.3 | 98 |
| 2012 | 5.7 | 117 |
| 2011 | 6.4 | 117 |
| 2010 | 1.7 | 142 |
| 2009 | 3.1 | 118 |
| 2008 | 10.6 | 100 |
| 2007 | 1.9 | 139 |
| 2006 | 2.7 | 121 |
| 2005 | 4.9 | 98 |
| 2004 | 8.4 | 71 |
| 2003 | 8.7 | 63 |
| 2002 | 7.8 | 60 |
| 2001 | 5.4 | 66 |
| 2000 | -.2 | 177 |
| 1999 | 6.5 | 56 |
| 1998 | 8.7 | 55 |
| 1997 | 7.2 | 55 |
| 1996 | 5 | 51 |
| 1995 | 4.5 | 49 |
| 1994 | 5.8 | 45 |
| 1993 | 4.7 | 47 |
| 1992 | 1.8 | 49 |
| 1991 | 1.6 | 49 |
| 1990 | 1.3 | 56 |
| 1989 | 1.6 | 45 |
| 1988 | 1.6 | 41 |
| 1987 | 1.2 | 36 |
| 1986 | 0.8 | 43 |