| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 17.7 | 55 |
| 2015 | 16.2 | 64 |
| 2014 | 15.5 | 65 |
| 2013 | 14.4 | 66 |
| 2012 | 14.7 | 66 |
| 2011 | 15.9 | 65 |
| 2010 | 15.6 | 62 |
| 2009 | 15.7 | 60 |
| 2008 | 13.6 | 67 |
| 2007 | 10.3 | 68 |
| 2006 | 7 | 74 |
| 2005 | 6 | 73 |
| 2004 | 5.9 | 73 |
| 2003 | 6.1 | 67 |
| 2002 | 5.2 | 66 |
| 2001 | 5.3 | 64 |
| 2000 | 5.3 | 65 |
| 1999 | 5.1 | 65 |
| 1998 | 5 | 65 |
| 1997 | 4.4 | 67 |
| 1996 | 4.2 | 64 |
| 1995 | 3 | 66 |
| 1994 | 4.1 | 61 |
| 1993 | 3.9 | 61 |
| 1992 | 3.7 | 57 |
| 1991 | 4.3 | 56 |
| 1990 | 3.2 | 64 |
| 1989 | 3.8 | 57 |
| 1988 | 5.9 | 52 |
| 1987 | 6.5 | 51 |
| 1986 | 6.3 | 45 |