Year current US$ 1995 6000000 1996 8000000 1997 5000000 1998 5000000 1999 11000000 2000 17000000 2001 21000000 2002 13000000 2003 25000000 2004 30000000 2005 24000000 2006 23000000 2007 19000000 2008 22000000 2009 21000000 2010 18000000 2011 18000000 2012 19000000 2013 22000000 2014 21000000 2015 15000000 2018 13000000 2019 10000000 2020 4000000