| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 2.9 | 95 |
| 2015 | 2.8 | 102 |
| 2014 | 2.8 | 103 |
| 2013 | 2.6 | 105 |
| 2012 | 2.4 | 103 |
| 2011 | 2.6 | 101 |
| 2010 | 2.7 | 98 |
| 2009 | 2.2 | 100 |
| 2008 | 2.4 | 102 |
| 2007 | 2.9 | 93 |
| 2006 | 2.5 | 93 |
| 2005 | 2.4 | 91 |
| 2004 | 2.3 | 87 |
| 2003 | 2 | 88 |
| 2002 | 1.5 | 89 |
| 2001 | 1.6 | 88 |
| 2000 | 1.3 | 91 |
| 1999 | 1.4 | 88 |
| 1998 | 1.4 | 86 |
| 1997 | 1.3 | 86 |
| 1996 | 1.4 | 81 |
| 1995 | 1.4 | 80 |
| 1994 | 1.3 | 81 |
| 1993 | 1.1 | 87 |
| 1992 | 1.2 | 82 |
| 1991 | 1.1 | 82 |
| 1990 | 1 | 85 |
| 1989 | 0.8 | 84 |
| 1988 | 0.9 | 83 |
| 1987 | 0.7 | 80 |
| 1986 | 0.5 | 75 |