Year Percent 2006-01-01 70.500 2007-01-01 70.525 2008-01-01 71.050 2009-01-01 71.400 2010-01-01 71.925 2011-01-01 72.950 2012-01-01 72.350 2013-01-01 72.900 2014-01-01 73.625 2015-01-01 73.925 2016-01-01 74.400 2017-01-01 74.750