Year Percent 2006 47.82047 2007 50.65979 2008 54.24649 2009 51.9344 2010 55.41489 2011 56.8934 2012 52.35714 2013 49.59176 2014 51.21688 2015 50.39178 2016 50.90927 2017 53.34651