| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 7.3 | 103 |
| 2014 | 0.5 | 162 |
| 2013 | 7 | 101 |
| 2012 | 14.3 | 86 |
| 2010 | 17.8 | 69 |
| 2009 | 13.7 | 78 |
| 2008 | 41.1 | 55 |
| 2007 | 46.9 | 56 |
| 2006 | 20.6 | 71 |
| 2005 | 10.4 | 76 |
| 2004 | 3.6 | 94 |
| 2003 | 1.4 | 111 |
| 2002 | 1.5 | 105 |
| 2001 | -1.3 | 185 |
| 2000 | 1.4 | 95 |
| 1999 | -1.3 | 180 |
| 1998 | -1.3 | 181 |
| 1997 | -.7 | 182 |
| 1996 | -1.1 | 179 |
| 1995 | -.9 | 175 |
| 1994 | -.7 | 172 |
| 1993 | 0.6 | 88 |
| 1992 | 1 | 67 |
| 1991 | 0.9 | 60 |
| 1990 | 1.6 | 47 |
| 1989 | 1.3 | 47 |
| 1988 | 1 | 47 |
| 1987 | -1 | 140 |
| 1986 | -1.8 | 142 |