| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 39.5 | 74 |
| 2015 | 38.9 | 89 |
| 2014 | 35.7 | 89 |
| 2013 | 33.4 | 92 |
| 2012 | 30.6 | 95 |
| 2011 | 29.1 | 94 |
| 2010 | 27.2 | 102 |
| 2009 | 26.4 | 96 |
| 2008 | 25.4 | 94 |
| 2007 | 24.4 | 93 |
| 2006 | 23.6 | 91 |
| 2005 | 22.8 | 88 |
| 2004 | 22.1 | 88 |
| 2003 | 21.4 | 87 |
| 2002 | 20.7 | 88 |
| 2001 | 20 | 90 |
| 2000 | 19.4 | 87 |
| 1999 | 19 | 85 |
| 1998 | 18.4 | 86 |
| 1997 | 17.7 | 89 |
| 1996 | 17.2 | 87 |
| 1995 | 16.7 | 88 |
| 1994 | 15.7 | 83 |
| 1993 | 15.2 | 83 |
| 1992 | 14.8 | 78 |
| 1991 | 14.3 | 79 |
| 1990 | 13.9 | 76 |
| 1989 | 13.9 | 66 |
| 1988 | 13.7 | 65 |
| 1987 | 13.2 | 64 |
| 1986 | 13.8 | 62 |