| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 24.8 | 50 |
| 2015 | 31.9 | 48 |
| 2014 | 29.3 | 52 |
| 2013 | 29.6 | 53 |
| 2012 | 25.5 | 55 |
| 2011 | 20.3 | 59 |
| 2010 | 19.6 | 57 |
| 2009 | 17.2 | 58 |
| 2008 | 13.8 | 66 |
| 2007 | 12.2 | 64 |
| 2006 | 12.2 | 59 |
| 2005 | 11.5 | 57 |
| 2004 | 9.2 | 59 |
| 2003 | 8.9 | 57 |
| 2002 | 8.4 | 56 |
| 2001 | 9 | 53 |
| 2000 | 9.1 | 53 |
| 1999 | 9.9 | 52 |
| 1998 | 11.4 | 52 |
| 1997 | 11.8 | 51 |
| 1996 | 14 | 48 |
| 1995 | 14.1 | 46 |
| 1994 | 11.1 | 47 |
| 1993 | 9.6 | 48 |
| 1992 | 9 | 48 |
| 1991 | 6.9 | 51 |
| 1990 | 7.1 | 55 |
| 1989 | 5.7 | 53 |
| 1988 | 3.8 | 56 |
| 1987 | 8.2 | 45 |
| 1986 | 6.1 | 46 |