| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 5.4 | 72 |
| 2015 | 5.2 | 80 |
| 2014 | 5.1 | 84 |
| 2013 | 4.4 | 84 |
| 2012 | 3.6 | 91 |
| 2011 | 3.1 | 95 |
| 2010 | 2.9 | 96 |
| 2009 | 2.2 | 102 |
| 2008 | 1.9 | 107 |
| 2007 | 1.7 | 107 |
| 2006 | 1.5 | 105 |
| 2005 | 1.4 | 103 |
| 2004 | 1.3 | 103 |
| 2003 | 1.3 | 101 |
| 2002 | 1.4 | 94 |
| 2001 | 1.5 | 89 |
| 2000 | 1.4 | 90 |
| 1999 | 1.3 | 89 |
| 1998 | 1.3 | 91 |
| 1997 | 1.2 | 89 |
| 1996 | 1 | 94 |
| 1995 | 0.9 | 92 |
| 1994 | 0.6 | 97 |
| 1993 | 0.6 | 98 |
| 1992 | 1 | 85 |
| 1991 | 1.1 | 81 |
| 1990 | 0.9 | 87 |
| 1989 | 1.1 | 76 |
| 1988 | 1.2 | 74 |