| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 7.6 | 65 |
| 2015 | 6.6 | 76 |
| 2014 | 8.4 | 76 |
| 2013 | 9 | 76 |
| 2012 | 8.1 | 77 |
| 2011 | 8.3 | 73 |
| 2010 | 8.9 | 71 |
| 2009 | 9.6 | 73 |
| 2008 | 10.4 | 74 |
| 2007 | 10.3 | 69 |
| 2006 | 7.5 | 71 |
| 2005 | 7 | 68 |
| 2004 | 6.5 | 69 |
| 2003 | 5.7 | 69 |
| 2002 | 4.6 | 69 |
| 2001 | 4.1 | 67 |
| 2000 | 3.5 | 70 |
| 1999 | 3.6 | 72 |
| 1998 | 3.2 | 71 |
| 1997 | 2.4 | 75 |
| 1996 | 2.1 | 72 |
| 1995 | 3.1 | 64 |
| 1994 | 2.4 | 70 |
| 1993 | 2.8 | 67 |
| 1992 | 3.1 | 61 |
| 1991 | 3.3 | 62 |
| 1990 | 7.9 | 51 |
| 1989 | 9.7 | 45 |