Year Percent 2006-01-01 76.925 2007-01-01 76.850 2008-01-01 75.975 2009-01-01 74.475 2010-01-01 72.875 2011-01-01 71.600 2012-01-01 70.975 2013-01-01 69.700 2014-01-01 69.775 2015-01-01 68.600 2016-01-01 67.600 2017-01-01 66.450