| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 3.4 | 90 |
| 2015 | 3.9 | 90 |
| 2014 | 4 | 94 |
| 2013 | 3.7 | 96 |
| 2012 | 3.2 | 98 |
| 2011 | 2.9 | 99 |
| 2010 | 2 | 104 |
| 2009 | 1.7 | 107 |
| 2008 | 1.7 | 110 |
| 2007 | 1.3 | 112 |
| 2006 | 1.1 | 114 |
| 2005 | 0.8 | 115 |
| 2004 | 0.8 | 112 |
| 2003 | 0.6 | 115 |
| 2002 | 0.7 | 105 |
| 2001 | 0.9 | 98 |
| 2000 | 1.1 | 95 |
| 1999 | 1.2 | 92 |
| 1998 | 1.4 | 88 |
| 1997 | 1.7 | 82 |
| 1996 | 2 | 73 |
| 1995 | 2.1 | 74 |
| 1994 | 1.6 | 76 |
| 1993 | 1.6 | 80 |
| 1992 | 1.7 | 72 |
| 1991 | 2 | 71 |
| 1990 | 1.1 | 84 |
| 1989 | 1 | 81 |
| 1988 | 1.2 | 76 |
| 1987 | 1 | 77 |
| 1986 | 1.3 | 64 |