| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 1.7 | 119 |
| 2015 | 2.9 | 142 |
| 2014 | 2.1 | 146 |
| 2013 | 2 | 151 |
| 2012 | 2 | 152 |
| 2011 | 2 | 153 |
| 2010 | 2.1 | 166 |
| 2009 | 2.5 | 150 |
| 2008 | 2.5 | 147 |
| 2007 | 2.1 | 146 |
| 2006 | 2 | 144 |
| 2005 | 1.9 | 138 |
| 2004 | 2 | 134 |
| 2003 | 1.9 | 134 |
| 2002 | 2.2 | 133 |
| 2001 | 1.9 | 131 |
| 2000 | 1.8 | 129 |
| 1999 | 1.8 | 125 |
| 1998 | 1.7 | 125 |
| 1997 | 1.5 | 125 |
| 1996 | 1.5 | 123 |
| 1995 | 1.4 | 122 |
| 1994 | 1.3 | 115 |
| 1993 | 1.2 | 114 |
| 1992 | 1.1 | 107 |
| 1991 | 1.1 | 104 |
| 1990 | 1.1 | 102 |
| 1989 | 1.1 | 89 |
| 1988 | 1.1 | 87 |
| 1987 | 0.9 | 87 |
| 1986 | 0.9 | 86 |