Year current US$ 1995 49000000 1996 40000000 1997 38000000 1998 38000000 1999 40000000 2000 40000000 2001 36000000 2002 36000000 2003 48000000 2004 66000000 2005 77000000 2006 120000000 2007 137000000 2008 147000000 2009 102000000 2010 111000000 2011 119000000 2012 102000000 2013 118000000 2014 144000000 2015 150000000 2016 157000000 2017 160000000 2018 179000000