| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 19.6 | 54 |
| 2015 | 17.6 | 63 |
| 2014 | 18.8 | 63 |
| 2013 | 20.8 | 61 |
| 2012 | 21.5 | 59 |
| 2011 | 24.7 | 52 |
| 2010 | 25 | 51 |
| 2009 | 27.2 | 51 |
| 2008 | 29.2 | 51 |
| 2007 | 27.1 | 46 |
| 2006 | 24.5 | 45 |
| 2005 | 24.4 | 42 |
| 2004 | 20.4 | 43 |
| 2003 | 18.9 | 44 |
| 2002 | 14.9 | 43 |
| 2001 | 11.8 | 46 |
| 2000 | 11.6 | 46 |
| 1999 | 12.1 | 47 |
| 1998 | 11.7 | 50 |
| 1997 | 9.9 | 54 |
| 1996 | 11.2 | 50 |
| 1995 | 10.7 | 51 |
| 1994 | 9.4 | 49 |
| 1993 | 8.2 | 51 |