| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 3 | 94 |
| 2015 | 3.7 | 94 |
| 2014 | 4.4 | 88 |
| 2013 | 3.8 | 94 |
| 2012 | 3.5 | 93 |
| 2011 | 3.1 | 96 |
| 2010 | 2.8 | 97 |
| 2009 | 2.2 | 101 |
| 2008 | 2.8 | 98 |
| 2007 | 2.3 | 97 |
| 2006 | 2.1 | 96 |
| 2005 | 1.4 | 102 |
| 2004 | 1 | 110 |
| 1999 | 0.6 | 107 |
| 1997 | 0.4 | 115 |
| 1996 | 0.4 | 117 |
| 1995 | 0.6 | 100 |
| 1994 | 0.6 | 96 |
| 1993 | 0.5 | 101 |
| 1992 | 0.9 | 86 |
| 1991 | 0.9 | 86 |
| 1990 | 1.2 | 81 |
| 1989 | 1.7 | 69 |
| 1988 | 0.9 | 82 |
| 1987 | 0.7 | 81 |
| 1986 | 0.6 | 74 |