| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | -4 | 193 |
| 2014 | 15 | 82 |
| 2013 | 16.9 | 70 |
| 2012 | 15 | 82 |
| 2011 | 25.7 | 62 |
| 2010 | 23 | 60 |
| 2009 | 27.5 | 57 |
| 2008 | 26.4 | 66 |
| 2007 | 16.9 | 84 |
| 2006 | 18.4 | 74 |
| 2005 | 11.6 | 72 |
| 2004 | 8.8 | 69 |
| 2003 | 6.4 | 70 |
| 2002 | 10.7 | 52 |
| 2001 | 11.1 | 48 |
| 2000 | 2.8 | 72 |
| 1999 | 2.9 | 79 |
| 1998 | 6.1 | 62 |
| 1997 | 2.6 | 79 |
| 1996 | 2.7 | 67 |
| 1992 | 0.3 | 85 |
| 1991 | 0.1 | 103 |
| 1990 | 0 | 132 |
| 1989 | 0.1 | 89 |
| 1988 | 0.1 | 87 |
| 1987 | 0 | 105 |
| 1986 | 0.1 | 89 |