Year Percent 2005-01-01 56.075 2006-01-01 56.100 2007-01-01 55.625 2008-01-01 55.600 2009-01-01 56.475 2010-01-01 57.750 2011-01-01 58.125 2012-01-01 58.550 2013-01-01 59.000 2014-01-01 59.875 2015-01-01 60.275 2016-01-01 60.350 2017-01-01 60.225