| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2016 | 27.7 | 85 |
| 2015 | 28.8 | 100 |
| 2014 | 28.7 | 99 |
| 2013 | 29.3 | 100 |
| 2012 | 27.9 | 99 |
| 2011 | 28.4 | 97 |
| 2010 | 28.6 | 99 |
| 2009 | 30.5 | 90 |
| 2008 | 24 | 97 |
| 2007 | 24.2 | 94 |
| 2006 | 23.1 | 92 |
| 2005 | 22 | 90 |
| 2004 | 20.9 | 90 |
| 2003 | 19.1 | 92 |
| 2002 | 19.1 | 91 |
| 2001 | 19.2 | 91 |
| 2000 | 18.9 | 90 |
| 1999 | 19.7 | 83 |
| 1998 | 19.1 | 83 |
| 1997 | 20.1 | 81 |
| 1996 | 20.1 | 81 |
| 1995 | 19.6 | 81 |
| 1994 | 20 | 73 |
| 1993 | 19.3 | 75 |
| 1992 | 19.5 | 69 |
| 1991 | 20.2 | 66 |
| 1990 | 20.3 | 64 |
| 1989 | 18.8 | 57 |
| 1988 | 19 | 57 |
| 1987 | 20.6 | 54 |
| 1986 | 20.8 | 53 |