| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 14 | 99 |
| 2015 | 13.5 | 118 |
| 2014 | 12.9 | 119 |
| 2013 | 13.1 | 122 |
| 2012 | 12.2 | 124 |
| 2011 | 12.3 | 123 |
| 2010 | 12.1 | 131 |
| 2009 | 11.6 | 121 |
| 2008 | 11.8 | 120 |
| 2007 | 12 | 116 |
| 2006 | 11.4 | 115 |
| 2005 | 10 | 116 |
| 2004 | 8.4 | 117 |
| 2003 | 7.6 | 117 |
| 2002 | 6.6 | 117 |
| 2001 | 6.5 | 115 |
| 2000 | 6.2 | 114 |
| 1999 | 6.1 | 109 |
| 1998 | 6 | 111 |
| 1997 | 6.1 | 108 |
| 1996 | 6.3 | 106 |
| 1995 | 6.4 | 106 |
| 1994 | 6.4 | 101 |
| 1993 | 6.6 | 96 |
| 1992 | 6.5 | 94 |
| 1991 | 7.4 | 89 |
| 1990 | 6.9 | 87 |