| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 1.6 | 143 |
| 2014 | 39.6 | 52 |
| 2013 | 9.4 | 90 |
| 2012 | 14.7 | 83 |
| 2011 | 14.2 | 82 |
| 2010 | 14.2 | 78 |
| 2009 | 32 | 51 |
| 2008 | 51.9 | 51 |
| 2007 | 45.7 | 58 |
| 2006 | 33 | 56 |
| 2005 | 17.9 | 63 |
| 2004 | 12.9 | 56 |
| 2003 | 18.3 | 45 |
| 2002 | 9.5 | 54 |
| 2001 | 9.8 | 50 |
| 2000 | 10.6 | 44 |
| 1999 | 14.5 | 41 |
| 1998 | 9.4 | 52 |
| 1997 | 5.4 | 59 |
| 1996 | 4.9 | 52 |
| 1995 | 1.1 | 82 |
| 1994 | 1.1 | 75 |
| 1993 | 1.4 | 66 |
| 1992 | 0.1 | 108 |