Year US Dollars 1995 19.02 1996 18.1 1997 18.35 1998 18.6 1999 18.56 2000 18.15 2001 18.28 2002 18.67 2003 18.67 2004 18.28 2005 18.83 2006 19.81 2007 20.14 2009 21.63 2010 22.31 2011 23.22 2012 25.71 2013 25.91 2014 26.39 2015 26.42 2016 27.08