| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 5 | 115 |
| 2014 | 6.6 | 105 |
| 2013 | 17.5 | 69 |
| 2012 | 10.6 | 96 |
| 2011 | 8.6 | 104 |
| 2010 | 6.2 | 102 |
| 2009 | 4.2 | 109 |
| 2008 | 5.1 | 121 |
| 2007 | 3.7 | 126 |
| 2006 | 2.8 | 119 |
| 2005 | -2.4 | 191 |
| 2004 | 0.7 | 140 |
| 2003 | 2 | 102 |
| 2002 | 6.8 | 65 |
| 2001 | 7.1 | 58 |
| 2000 | 7.4 | 58 |
| 1999 | 10.1 | 49 |
| 1998 | 9.5 | 51 |
| 1997 | 7.3 | 54 |
| 1996 | 4.7 | 53 |
| 1995 | 3.9 | 54 |
| 1994 | 1.3 | 71 |
| 1993 | 1.2 | 70 |
| 1992 | 0.9 | 69 |
| 1991 | 0.5 | 72 |
| 1990 | 0.3 | 86 |
| 1989 | -.2 | 139 |
| 1988 | -.1 | 135 |
| 1987 | 0.7 | 51 |
| 1986 | 0.2 | 65 |