| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 4.3 | 79 |
| 2015 | 4.5 | 86 |
| 2014 | 4.6 | 87 |
| 2013 | 4.4 | 83 |
| 2012 | 3.8 | 89 |
| 2011 | 3.9 | 86 |
| 2010 | 4 | 85 |
| 2009 | 3.6 | 90 |
| 2008 | 4 | 89 |
| 2007 | 2.8 | 94 |
| 2006 | 1.9 | 99 |
| 2005 | 1.4 | 101 |
| 2004 | 1 | 111 |
| 2003 | 0.8 | 111 |
| 2002 | 0.6 | 107 |
| 2001 | 0.7 | 104 |
| 2000 | 0.7 | 102 |
| 1999 | 0.7 | 102 |
| 1998 | 0.7 | 101 |
| 1997 | 0.6 | 106 |
| 1996 | 0.5 | 104 |
| 1995 | 0.6 | 96 |
| 1993 | 0.3 | 122 |
| 1992 | 0.3 | 110 |