| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 5.7 | 53 |
| 2015 | 3 | 130 |
| 2014 | 0.6 | 159 |
| 2013 | 4 | 119 |
| 2012 | 3.4 | 132 |
| 2011 | 5.1 | 122 |
| 2010 | 3 | 124 |
| 2009 | 2.6 | 120 |
| 2008 | 6.1 | 119 |
| 2007 | 7.3 | 104 |
| 2006 | 4.3 | 107 |
| 2005 | 1.5 | 128 |
| 2004 | 3.1 | 101 |
| 2003 | 1.2 | 118 |
| 2002 | 1.1 | 110 |
| 2001 | 4.7 | 69 |
| 2000 | 2.2 | 83 |
| 1999 | 0.9 | 108 |
| 1998 | 1.5 | 102 |
| 1997 | 0.2 | 148 |
| 1996 | 0.1 | 144 |
| 1995 | 0.1 | 137 |
| 1994 | 0.2 | 111 |