| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 30.7 | 37 |
| 2015 | 11.4 | 89 |
| 2014 | 27 | 59 |
| 2013 | 29.5 | 53 |
| 2012 | 16.6 | 78 |
| 2011 | 10.9 | 92 |
| 2010 | 5.3 | 106 |
| 2009 | 27.6 | 56 |
| 2008 | 57.3 | 49 |
| 2007 | 19.6 | 77 |
| 2006 | 54.1 | 46 |
| 2005 | 6.9 | 88 |
| 2004 | 21.5 | 46 |
| 2003 | 14.1 | 53 |
| 2002 | 0.3 | 137 |
| 2001 | 0 | 164 |
| 2000 | -.1 | 175 |
| 1999 | 5.7 | 59 |
| 1997 | 9.8 | 50 |
| 1996 | 10.6 | 43 |
| 1995 | 10.5 | 38 |
| 1994 | 9.8 | 35 |
| 1993 | 9.8 | 33 |
| 1992 | 11.4 | 24 |
| 1991 | 11.4 | 27 |
| 1990 | 10.1 | 24 |
| 1989 | 7.5 | 27 |
| 1988 | 9.1 | 23 |
| 1987 | 6.8 | 19 |
| 1986 | 4.7 | 21 |