| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 4.9 | 75 |
| 2015 | 4.5 | 85 |
| 2014 | 4.3 | 90 |
| 2013 | 3.8 | 92 |
| 2012 | 3.8 | 90 |
| 2011 | 3.5 | 91 |
| 2010 | 3.4 | 91 |
| 2009 | 3.8 | 87 |
| 2008 | 4 | 88 |
| 2007 | 3.7 | 88 |
| 2006 | 3.5 | 86 |
| 2005 | 3.4 | 81 |
| 2004 | 3.1 | 81 |
| 2003 | 2.8 | 79 |
| 2002 | 2.9 | 76 |
| 2001 | 3.6 | 72 |
| 2000 | 6.2 | 61 |
| 1999 | 7.4 | 59 |
| 1998 | 4.7 | 67 |
| 1997 | 2.3 | 77 |
| 1996 | 1.3 | 86 |
| 1995 | 1.2 | 85 |
| 1994 | 1.4 | 78 |
| 1993 | 1.9 | 77 |
| 1992 | 2.6 | 66 |
| 1991 | 5.3 | 55 |
| 1990 | 7.9 | 53 |
| 1989 | 7.8 | 52 |
| 1988 | 6.1 | 51 |
| 1987 | 4.8 | 53 |
| 1986 | 4.4 | 48 |