| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 17.5 | 56 |
| 2015 | 20.1 | 61 |
| 2014 | 23.6 | 56 |
| 2013 | 24.2 | 58 |
| 2012 | 23.2 | 56 |
| 2011 | 23.8 | 54 |
| 2010 | 19.9 | 56 |
| 2009 | 15 | 62 |
| 2008 | 16.2 | 60 |
| 2007 | 9.7 | 72 |
| 2006 | 7.8 | 70 |
| 2005 | 6.7 | 70 |
| 2004 | 6.4 | 70 |
| 2003 | 5.9 | 68 |
| 2002 | 9 | 55 |
| 2001 | 5.7 | 61 |
| 2000 | 3.7 | 68 |
| 1999 | 4.9 | 66 |
| 1998 | 2.9 | 75 |
| 1997 | 2.2 | 78 |
| 1996 | 1.9 | 74 |
| 1995 | 2 | 75 |
| 1994 | 1.3 | 80 |
| 1993 | 1.4 | 83 |
| 1992 | 1.6 | 73 |
| 1991 | 2 | 70 |
| 1990 | 2.4 | 67 |
| 1989 | 1.3 | 72 |
| 1988 | 1.9 | 67 |
| 1987 | 1.7 | 66 |
| 1986 | 2.5 | 53 |