Year Percent 2003-01-01 56.750 2004-01-01 56.675 2005-01-01 56.725 2006-01-01 56.800 2007-01-01 57.525 2008-01-01 58.100 2009-01-01 57.375 2010-01-01 57.300 2011-01-01 57.150 2012-01-01 57.025 2013-01-01 56.725 2014-01-01 56.150 2015-01-01 56.050 2016-01-01 56.100 2017-01-01 56.300