| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 23.2 | 40 |
| 2015 | 32.5 | 55 |
| 2014 | 35.3 | 54 |
| 2013 | 33.6 | 48 |
| 2012 | 28.4 | 65 |
| 2011 | 25.2 | 63 |
| 2010 | 12.4 | 85 |
| 2009 | 19.7 | 64 |
| 2008 | 24.7 | 69 |
| 2007 | 28.1 | 67 |
| 2006 | 23.7 | 67 |
| 2005 | 16.2 | 66 |
| 2004 | 7.9 | 74 |
| 2003 | 23.1 | 40 |
| 2002 | 0.8 | 119 |
| 2001 | 1.4 | 101 |
| 2000 | 2.2 | 82 |
| 1999 | 0 | 159 |
| 1998 | 0.1 | 151 |
| 1997 | 0 | 161 |
| 1996 | 0.8 | 105 |
| 1995 | 0.9 | 91 |
| 1994 | 5.5 | 46 |
| 1993 | 4.9 | 46 |
| 1992 | 4.2 | 40 |
| 1991 | 3.2 | 39 |
| 1990 | 1.7 | 44 |
| 1989 | 1.7 | 42 |
| 1988 | 0.8 | 54 |
| 1987 | 0.6 | 53 |
| 1986 | 0 | 109 |