| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 1.8 | 62 |
| 2015 | 7.6 | 102 |
| 2014 | 10.8 | 87 |
| 2013 | 9.9 | 86 |
| 2012 | 10.8 | 93 |
| 2011 | 15 | 80 |
| 2010 | 4.4 | 115 |
| 2009 | -.3 | 186 |
| 2008 | 14.3 | 90 |
| 2007 | 27.1 | 68 |
| 2006 | 17 | 76 |
| 2005 | 8.1 | 83 |
| 2004 | 5.9 | 81 |
| 2003 | 3.2 | 92 |
| 2002 | 1.6 | 100 |
| 2001 | 1.7 | 92 |
| 2000 | 3.2 | 69 |
| 1999 | 3.5 | 74 |
| 1998 | 3.6 | 72 |
| 1997 | 5.2 | 60 |
| 1996 | 3.8 | 56 |
| 1995 | 1.8 | 68 |
| 1994 | 2.1 | 60 |
| 1993 | 0.5 | 95 |
| 1992 | 0.3 | 86 |