Year US Dollars 2000 25.44 2001 25.57 2002 26.74 2003 27.89 2004 28.63 2005 28.98 2006 30.08 2007 30.13 2008 30.9 2009 33.01 2010 33.41 2011 34.57 2012 36.5 2013 38.39 2014 39.31 2015 40.55 2016 40.85