| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 31.8 | 36 |
| 2015 | 31.5 | 57 |
| 2014 | 32.8 | 57 |
| 2013 | 32.1 | 50 |
| 2012 | 27 | 68 |
| 2011 | 27.3 | 60 |
| 2010 | 19.1 | 65 |
| 2009 | 16.1 | 70 |
| 2008 | 24.4 | 70 |
| 2007 | 22.4 | 74 |
| 2006 | 18 | 75 |
| 2005 | 15.3 | 70 |
| 2004 | 10.8 | 63 |
| 2003 | 7.7 | 66 |
| 2002 | 7.2 | 62 |
| 2001 | 6.2 | 59 |
| 2000 | 7.2 | 59 |
| 1999 | 6.2 | 58 |
| 1998 | 6.1 | 61 |
| 1997 | 4.1 | 67 |
| 1996 | 4.3 | 54 |
| 1995 | 3.4 | 55 |
| 1994 | 3 | 56 |
| 1993 | 2.5 | 57 |
| 1992 | 2.3 | 46 |
| 1991 | 1.8 | 47 |
| 1990 | 1.6 | 46 |
| 1989 | 1 | 50 |
| 1988 | 1.2 | 45 |
| 1987 | 0.8 | 49 |
| 1986 | 0.6 | 48 |