| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 3.4 | 58 |
| 2015 | 1.8 | 139 |
| 2014 | 4 | 125 |
| 2013 | 3.5 | 126 |
| 2012 | 5 | 123 |
| 2011 | 6.5 | 115 |
| 2010 | 5.3 | 107 |
| 2009 | 7.6 | 92 |
| 2008 | 9.4 | 103 |
| 2007 | 6.7 | 110 |
| 2006 | 4.7 | 104 |
| 2005 | 2.9 | 109 |
| 2004 | 2.5 | 110 |
| 2003 | 1.2 | 117 |
| 2002 | 1.1 | 111 |
| 2001 | 0.7 | 119 |
| 2000 | 1 | 110 |
| 1999 | 1.2 | 101 |
| 1998 | 2.2 | 85 |
| 1997 | 0.5 | 126 |
| 1996 | 0.2 | 134 |
| 1995 | 0.3 | 121 |
| 1994 | 0.1 | 134 |
| 1993 | 0 | 151 |
| 1992 | 0 | 132 |