Year Percent 2005-01-01 77.500 2006-01-01 78.200 2007-01-01 79.200 2008-01-01 79.000 2009-01-01 77.900 2010-01-01 76.550 2011-01-01 77.225 2012-01-01 76.975 2013-01-01 76.350 2014-01-01 76.325 2015-01-01 76.475 2016-01-01 76.625 2017-01-01 77.150