Year Percent 2003-01-01 52.200 2004-01-01 52.200 2005-01-01 53.100 2006-01-01 52.400 2007-01-01 53.650 2008-01-01 53.150 2009-01-01 55.175 2010-01-01 55.175 2011-01-01 54.775 2012-01-01 55.725 2013-01-01 55.925 2014-01-01 56.550 2015-01-01 56.000 2016-01-01 55.200 2017-01-01 56.050