| 时间 | 值 （亿美元） | 世界排名 |
|---|---|---|
| 2015 | -.5 | 189 |
| 2014 | 0.1 | 181 |
| 2013 | 0.3 | 167 |
| 2012 | 0.2 | 181 |
| 2011 | 0 | 185 |
| 2010 | -.1 | 189 |
| 2009 | 0.1 | 173 |
| 2008 | 0.1 | 182 |
| 2007 | 0.1 | 185 |
| 2006 | 0 | 181 |
| 2005 | 0 | 175 |
| 2004 | 0 | 174 |
| 2003 | 1.4 | 113 |
| 2002 | -.7 | 188 |
| 2001 | 2.5 | 86 |
| 2000 | 1.3 | 103 |
| 1999 | 0 | 172 |
| 1998 | 0 | 175 |
| 1997 | 0 | 173 |
| 1996 | 0 | 171 |
| 1995 | 0 | 166 |
| 1994 | 0 | 161 |
| 1993 | 0 | 155 |
| 1992 | 0 | 148 |
| 1991 | 0 | 138 |
| 1990 | 0 | 138 |