| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 12.7 | 85 |
| 2014 | 20.1 | 69 |
| 2013 | 18.1 | 68 |
| 2012 | 15.1 | 81 |
| 2011 | 14.9 | 81 |
| 2010 | 16.9 | 73 |
| 2009 | 24.1 | 59 |
| 2008 | 28.3 | 62 |
| 2007 | 26.2 | 70 |
| 2006 | 35.4 | 53 |
| 2005 | 19.8 | 60 |
| 2004 | 9.4 | 66 |
| 2003 | 5.5 | 73 |
| 2002 | 2.4 | 89 |
| 2001 | 2.7 | 82 |
| 2000 | 9.1 | 51 |
| 1999 | 1.6 | 94 |
| 1998 | 3.1 | 77 |
| 1997 | 3.6 | 69 |
| 1996 | 0.2 | 141 |
| 1995 | 0.1 | 130 |
| 1994 | 0 | 142 |
| 1993 | -.3 | 168 |
| 1992 | 0.4 | 80 |
| 1991 | -.1 | 150 |
| 1990 | 0.4 | 81 |
| 1989 | 0 | 131 |
| 1988 | 0.2 | 72 |
| 1987 | 0.4 | 61 |
| 1986 | 0.2 | 59 |