| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 30.5 | 82 |
| 2015 | 30 | 96 |
| 2014 | 28.8 | 97 |
| 2013 | 27.1 | 104 |
| 2012 | 25.7 | 103 |
| 2011 | 24.3 | 103 |
| 2010 | 23 | 107 |
| 2009 | 21.8 | 101 |
| 2008 | 19.2 | 104 |
| 2007 | 18.7 | 101 |
| 2006 | 16.2 | 102 |
| 2005 | 15.4 | 99 |
| 2004 | 14.2 | 101 |
| 2003 | 13.5 | 100 |
| 2002 | 12.6 | 103 |
| 2001 | 12.1 | 103 |
| 2000 | 12 | 99 |
| 1999 | 13.9 | 94 |
| 1998 | 12.3 | 97 |
| 1997 | 12 | 95 |
| 1996 | 11.5 | 95 |
| 1995 | 11 | 95 |
| 1994 | 10.3 | 91 |
| 1993 | 9.6 | 90 |
| 1992 | 9 | 88 |
| 1991 | 9.3 | 85 |
| 1990 | 8.3 | 85 |
| 1989 | 7 | 75 |
| 1988 | 6.1 | 75 |
| 1987 | 5 | 77 |
| 1986 | 4.1 | 78 |