Year Percent 2005-01-01 51.250 2006-01-01 51.925 2007-01-01 52.650 2008-01-01 52.825 2009-01-01 51.600 2010-01-01 51.125 2011-01-01 51.100 2012-01-01 50.650 2013-01-01 50.200 2014-01-01 50.300 2015-01-01 50.650 2016-01-01 51.375 2017-01-01 52.000