Year % of total 2006 74.58825334821428 2007 76.11570559147964 2008 69.16954625121713 2009 66.91281708094327 2010 66.1097385340763 2011 67.51581381617792 2012 66.31259185918591 2013 67.84943228602384 2014 63.651619318181815 2015 67.74530779450842 2016 67.24155060553633