| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | 36.5 | 91 |
| 2014 | 34.8 | 91 |
| 2013 | 32.5 | 95 |
| 2012 | 30.5 | 97 |
| 2011 | 28.9 | 95 |
| 2010 | 27.4 | 101 |
| 2009 | 25.3 | 97 |
| 2008 | 24.2 | 96 |
| 2007 | 22.7 | 95 |
| 2006 | 20.9 | 98 |
| 2005 | 20.3 | 94 |
| 2004 | 20.1 | 93 |
| 2003 | 19.4 | 90 |
| 2002 | 18.7 | 92 |
| 2001 | 18.1 | 94 |
| 2000 | 17.1 | 92 |
| 1999 | 16.1 | 89 |
| 1998 | 15.1 | 90 |
| 1997 | 14.3 | 93 |
| 1996 | 14 | 93 |
| 1995 | 13.6 | 93 |
| 1994 | 12.8 | 88 |
| 1993 | 13.2 | 86 |
| 1992 | 13.9 | 81 |
| 1991 | 16.7 | 72 |
| 1990 | 15.3 | 74 |
| 1989 | 13.6 | 67 |
| 1988 | 13.9 | 64 |
| 1987 | 16 | 61 |
| 1986 | 15.7 | 60 |