| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 23.8 | 90 |
| 2015 | 23 | 107 |
| 2014 | 22 | 108 |
| 2013 | 21.1 | 110 |
| 2012 | 20.8 | 112 |
| 2011 | 20.2 | 111 |
| 2010 | 19.2 | 115 |
| 2009 | 18.7 | 104 |
| 2008 | 18.4 | 105 |
| 2007 | 18.2 | 102 |
| 2006 | 17 | 100 |
| 2005 | 16.2 | 97 |
| 2004 | 15.4 | 97 |
| 2003 | 14.6 | 98 |
| 2002 | 14.2 | 97 |
| 2001 | 13.7 | 98 |
| 2000 | 13.5 | 98 |
| 1999 | 13.5 | 95 |
| 1998 | 12.4 | 96 |
| 1997 | 12.3 | 94 |
| 1996 | 11.9 | 94 |
| 1995 | 11.7 | 94 |
| 1994 | 11.6 | 89 |
| 1993 | 12 | 87 |
| 1992 | 12.2 | 85 |
| 1991 | 12.2 | 83 |
| 1990 | 12.3 | 82 |
| 1989 | 12.2 | 68 |
| 1988 | 12.1 | 68 |
| 1987 | 11.9 | 67 |
| 1986 | 11.3 | 68 |