| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 33.5 | 78 |
| 2015 | 31.6 | 95 |
| 2014 | 28.6 | 100 |
| 2013 | 27 | 105 |
| 2012 | 20.5 | 113 |
| 2011 | 19.6 | 112 |
| 2010 | 18.5 | 119 |
| 2009 | 17.4 | 108 |
| 2008 | 17.3 | 108 |
| 2007 | 16.8 | 104 |
| 2006 | 15.8 | 104 |
| 2005 | 14.1 | 103 |
| 2004 | 12.9 | 105 |
| 2003 | 12 | 106 |
| 2002 | 11.6 | 106 |
| 2001 | 13.1 | 100 |
| 2000 | 11.7 | 100 |
| 1999 | 10.1 | 100 |
| 1998 | 11.8 | 98 |
| 1997 | 11.1 | 99 |
| 1996 | 11 | 98 |
| 1995 | 10.5 | 97 |
| 1994 | 10.3 | 92 |
| 1993 | 8.9 | 92 |
| 1992 | 9.1 | 87 |
| 1991 | 9.2 | 86 |
| 1990 | 8.7 | 83 |
| 1989 | 8.4 | 72 |
| 1988 | 8.5 | 71 |
| 1987 | 8.1 | 72 |
| 1986 | 7.6 | 70 |