Year Percent 2005-01-01 51.800 2006-01-01 52.500 2007-01-01 53.125 2008-01-01 53.475 2009-01-01 52.300 2010-01-01 51.875 2011-01-01 51.825 2012-01-01 51.575 2013-01-01 51.350 2014-01-01 51.725 2015-01-01 52.175 2016-01-01 52.800 2017-01-01 53.525