| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 0.9 | 157 |
| 2014 | 3.4 | 134 |
| 2013 | 20.6 | 65 |
| 2012 | 42.7 | 51 |
| 2011 | 45.7 | 48 |
| 2010 | 16.9 | 72 |
| 2009 | 6.2 | 101 |
| 2008 | 8.4 | 108 |
| 2007 | 3.7 | 125 |
| 2006 | 2.5 | 126 |
| 2005 | 1.9 | 122 |
| 2004 | 0.9 | 128 |
| 2003 | 1.3 | 115 |
| 2002 | 0.8 | 120 |
| 2001 | 0.4 | 129 |
| 2000 | 0.5 | 125 |
| 1999 | 0.3 | 139 |
| 1998 | 0.2 | 143 |
| 1997 | 0.3 | 137 |
| 1996 | 0.2 | 139 |
| 1995 | 0.1 | 135 |
| 1994 | 0.1 | 136 |
| 1993 | 0.1 | 134 |
| 1992 | 0 | 135 |
| 1991 | 0.1 | 104 |
| 1986 | 0 | 112 |