| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 20.9 | 52 |
| 2015 | 19.4 | 62 |
| 2014 | 22.7 | 60 |
| 2013 | 21.3 | 60 |
| 2012 | 20.9 | 61 |
| 2011 | 20.8 | 58 |
| 2010 | 19.3 | 58 |
| 2009 | 16.2 | 59 |
| 2008 | 16.6 | 58 |
| 2007 | 17.1 | 57 |
| 2006 | 14.6 | 55 |
| 2005 | 13.9 | 53 |
| 2004 | 13 | 52 |
| 2003 | 11.9 | 53 |
| 2002 | 9.2 | 53 |
| 2001 | 7.9 | 56 |
| 2000 | 8.3 | 55 |
| 1999 | 9.5 | 54 |
| 1998 | 9.5 | 54 |
| 1997 | 11.3 | 52 |
| 1996 | 12.5 | 49 |
| 1995 | 11.6 | 50 |
| 1994 | 10.1 | 48 |
| 1993 | 8.9 | 50 |
| 1992 | 8.6 | 49 |
| 1991 | 9.6 | 45 |
| 1990 | 10.6 | 44 |
| 1989 | 9.5 | 47 |
| 1988 | 9.5 | 45 |
| 1987 | 9.7 | 43 |
| 1986 | 7 | 43 |