| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 14.3 | 65 |
| 2014 | 14.8 | 66 |
| 2013 | 13.5 | 67 |
| 2012 | 11.8 | 68 |
| 2011 | 10.3 | 71 |
| 2010 | 8.4 | 73 |
| 2009 | 8.3 | 74 |
| 2008 | 7.2 | 79 |
| 2007 | 6.4 | 78 |
| 2006 | 5.7 | 78 |
| 2005 | 5.1 | 76 |
| 2004 | 5.3 | 74 |
| 2003 | 5.2 | 72 |
| 2002 | 4.4 | 71 |
| 2001 | 3.7 | 71 |
| 2000 | 3.6 | 69 |
| 1999 | 3.6 | 70 |
| 1998 | 3.3 | 70 |
| 1997 | 3.2 | 71 |
| 1996 | 3.2 | 68 |
| 1995 | 3 | 65 |
| 1994 | 2.8 | 67 |
| 1993 | 2.8 | 68 |
| 1992 | 2.8 | 64 |
| 1991 | 2.6 | 65 |
| 1990 | 2.4 | 68 |
| 1989 | 2.2 | 64 |
| 1988 | 2.1 | 65 |