Year current US$ 1995 72000000 1996 53000000 1997 53000000 1998 54000000 1999 54000000 2000 47000000 2001 43000000 2002 43000000 2003 55000000 2004 57000000 2005 65000000 2006 54000000 2007 253000000 2008 176000000 2009 157000000 2010 160000000 2011 151000000 2012 144000000 2013 150000000 2014 148000000 2015 133000000 2016 147000000 2017 154000000 2018 171000000