| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 3.5 | 89 |
| 2015 | 3.3 | 98 |
| 2014 | 3.6 | 97 |
| 2013 | 3.8 | 91 |
| 2012 | 4.1 | 84 |
| 2011 | 4.8 | 81 |
| 2010 | 4.8 | 82 |
| 2009 | 4.7 | 83 |
| 2008 | 4.5 | 87 |
| 2007 | 4 | 86 |
| 2006 | 3.8 | 82 |
| 2005 | 3.8 | 79 |
| 2004 | 3.4 | 78 |
| 2003 | 2.9 | 78 |
| 2002 | 2.4 | 79 |
| 2001 | 3.3 | 74 |
| 2000 | 2.8 | 74 |
| 1999 | 2.9 | 74 |
| 1998 | 4.8 | 66 |
| 1997 | 5.3 | 64 |
| 1996 | 4.5 | 62 |
| 1995 | 3 | 67 |
| 1994 | 3 | 64 |
| 1993 | 2.7 | 71 |
| 1992 | 6.3 | 52 |
| 1991 | 4.2 | 57 |
| 1990 | 4.1 | 60 |
| 1989 | 2.5 | 61 |
| 1988 | 2.4 | 62 |
| 1987 | 2 | 63 |
| 1986 | 0.5 | 80 |