| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 4 | 83 |
| 2015 | 4.2 | 88 |
| 2014 | 5.3 | 81 |
| 2013 | 4.1 | 88 |
| 2012 | 4.1 | 86 |
| 2011 | 4.2 | 84 |
| 2010 | 3.9 | 86 |
| 2009 | 3.5 | 91 |
| 2008 | 3.6 | 91 |
| 2007 | 3.2 | 90 |
| 2006 | 2.9 | 88 |
| 2005 | 2.5 | 90 |
| 2004 | 2 | 94 |
| 2003 | 2.4 | 82 |
| 2002 | 2.3 | 81 |
| 2001 | 2.2 | 80 |
| 2000 | 2.4 | 77 |
| 1999 | 2.6 | 79 |
| 1998 | 2.9 | 74 |
| 1997 | 3.7 | 69 |
| 1996 | 3.3 | 67 |
| 1995 | 2.9 | 68 |
| 1994 | 2.6 | 68 |
| 1993 | 2.3 | 75 |
| 1992 | 2.5 | 67 |
| 1991 | 2.5 | 67 |
| 1990 | 2.3 | 69 |
| 1989 | 1.9 | 67 |
| 1988 | 1.8 | 69 |
| 1987 | 1 | 72 |
| 1986 | 1.1 | 67 |