| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 5.7 | 70 |
| 2015 | 5.8 | 77 |
| 2014 | 6.3 | 79 |
| 2013 | 5.6 | 80 |
| 2012 | 5 | 80 |
| 2011 | 4 | 85 |
| 2010 | 3.3 | 93 |
| 2009 | 3.5 | 92 |
| 2008 | 3.3 | 95 |
| 2007 | 2.2 | 99 |
| 2006 | 1.8 | 100 |
| 2005 | 1.7 | 98 |
| 2004 | 1.7 | 96 |
| 2003 | 1.7 | 95 |
| 2002 | 1.6 | 87 |
| 2001 | 1.8 | 84 |
| 2000 | 1.7 | 82 |
| 1999 | 1.8 | 81 |
| 1998 | 2.3 | 79 |
| 1997 | 1.8 | 80 |
| 1996 | 1.5 | 80 |
| 1995 | 1.4 | 81 |
| 1994 | 1.3 | 79 |
| 1993 | 1.1 | 86 |
| 1992 | 1.4 | 77 |
| 1991 | 1.4 | 78 |
| 1990 | 1.4 | 78 |
| 1989 | 1 | 79 |
| 1988 | 0.9 | 81 |
| 1987 | 1 | 74 |
| 1986 | 0.9 | 70 |