Year Percent 2005-01-01 31.5930627992344 2006-01-01 31.8325053057012 2007-01-01 32.1170133302306 2008-01-01 34.1878219878896 2009-01-01 33.3085729755038 2010-01-01 37.4879512315087 2011-01-01 38.4247020042467 2012-01-01 37.1217968078470 2013-01-01 36.2712461782103 2014-01-01 36.0059849245949 2015-01-01 35.7353664960639 2016-01-01 34.5737836880271 2017-01-01 34.0483927584901