| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 14.9 | 80 |
| 2014 | 55 | 41 |
| 2013 | 29.1 | 54 |
| 2012 | 21.5 | 72 |
| 2011 | 21.8 | 68 |
| 2010 | 9.3 | 89 |
| 2009 | 12.7 | 81 |
| 2008 | 20.3 | 77 |
| 2007 | 26.4 | 69 |
| 2006 | 14.9 | 80 |
| 2005 | 8 | 84 |
| 2004 | 0.9 | 129 |
| 2003 | 2.2 | 98 |
| 2002 | 2 | 94 |
| 2001 | -1.4 | 186 |
| 2000 | -1 | 179 |
| 1999 | 5.4 | 60 |
| 1998 | 0.3 | 133 |
| 1997 | 0.8 | 113 |
| 1996 | 0.7 | 106 |
| 1995 | 1.3 | 76 |
| 1994 | 0 | 141 |
| 1993 | 2.9 | 56 |
| 1992 | 0 | 130 |
| 1991 | 0.3 | 80 |
| 1990 | 0.2 | 88 |
| 1989 | -.1 | 136 |
| 1988 | 0.1 | 95 |
| 1987 | 0.4 | 60 |
| 1986 | 0.2 | 61 |