| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 15.8 | 77 |
| 2014 | 15.1 | 80 |
| 2013 | 21 | 62 |
| 2012 | 17.3 | 77 |
| 2011 | 11.1 | 91 |
| 2010 | 17.3 | 70 |
| 2009 | 6.9 | 96 |
| 2008 | 9.4 | 104 |
| 2007 | 13.2 | 90 |
| 2006 | 6.2 | 97 |
| 2005 | 3.6 | 105 |
| 2004 | 3.6 | 92 |
| 2003 | 3.5 | 87 |
| 2002 | 3 | 82 |
| 2001 | 1.5 | 100 |
| 2000 | 1.2 | 104 |
| 1999 | 1.6 | 93 |
| 1998 | 2 | 93 |
| 1997 | 2.1 | 85 |
| 1996 | 1.2 | 88 |
| 1995 | 1 | 87 |
| 1994 | 0.4 | 99 |
| 1993 | 3.1 | 54 |
| 1992 | 0.5 | 77 |
| 1991 | 0.3 | 79 |
| 1990 | 2 | 42 |
| 1989 | 1.6 | 43 |
| 1988 | 0.9 | 48 |
| 1987 | 0.7 | 50 |
| 1986 | 0.3 | 56 |