| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 21.6 | 51 |
| 2015 | 24.5 | 56 |
| 2014 | 27.9 | 54 |
| 2013 | 27.4 | 54 |
| 2012 | 25.9 | 54 |
| 2011 | 24.5 | 53 |
| 2010 | 20.9 | 54 |
| 2009 | 19.5 | 56 |
| 2008 | 16.5 | 59 |
| 2007 | 13.1 | 62 |
| 2006 | 9.5 | 64 |
| 2005 | 9.5 | 63 |
| 2004 | 7.1 | 67 |
| 2003 | 7.4 | 62 |
| 2002 | 5.1 | 67 |
| 2001 | 3.8 | 70 |
| 2000 | 2.7 | 75 |
| 1999 | 3 | 73 |
| 1998 | 5.5 | 63 |
| 1997 | 5 | 65 |
| 1996 | 4.2 | 63 |
| 1995 | 4.8 | 61 |
| 1994 | 2.9 | 66 |
| 1993 | 2.8 | 70 |
| 1992 | 2.1 | 68 |
| 1991 | 2.1 | 69 |
| 1990 | 2 | 71 |
| 1989 | 1.9 | 66 |
| 1988 | 2 | 66 |
| 1987 | 2.1 | 62 |
| 1986 | 2.1 | 55 |