Year Percent 2005-01-01 77.6096237723036 2006-01-01 77.9973629967427 2007-01-01 77.5724298845259 2008-01-01 76.9222782820731 2009-01-01 74.7699032578944 2010-01-01 74.4691556267773 2011-01-01 74.3811670609467 2012-01-01 74.9212281868323 2013-01-01 74.6319292060715 2014-01-01 74.4967331467905 2015-01-01 74.6705471312230 2016-01-01 74.7279395054636 2017-01-01 75.0022602049821