Year Percent 2008-01-01 3.8716300000000000 2009-01-01 4.5447200000000000 2010-01-01 4.0483600000000000 2011-01-01 3.4720600000000000 2012-01-01 3.1764200000000002 2013-01-01 3.0307600000000000 2014-01-01 2.9954800000000000 2015-01-01 3.5046199999999996 2016-01-01 3.4318000000000000