| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 23.5 | 62 |
| 2014 | 20 | 70 |
| 2013 | 20.6 | 66 |
| 2012 | 12.8 | 90 |
| 2011 | 49.3 | 47 |
| 2010 | 16.9 | 71 |
| 2009 | 29.3 | 53 |
| 2008 | 40.6 | 56 |
| 2007 | 44.2 | 59 |
| 2006 | 42.6 | 52 |
| 2005 | 15.8 | 67 |
| 2004 | 9.6 | 65 |
| 2003 | 14.7 | 50 |
| 2002 | 4.9 | 71 |
| 2001 | 1.8 | 91 |
| 2000 | 0.5 | 127 |
| 1999 | 1.1 | 104 |
| 1998 | 1.1 | 108 |
| 1997 | 7.4 | 53 |
| 1996 | 0 | 169 |
| 1995 | 0.4 | 108 |
| 1994 | 0.6 | 91 |
| 1993 | 1 | 76 |
| 1992 | 1.3 | 57 |