Year Percent 2005-01-01 40.525 2006-01-01 41.750 2007-01-01 43.300 2008-01-01 44.375 2009-01-01 45.150 2010-01-01 45.725 2011-01-01 46.975 2012-01-01 48.550 2013-01-01 49.975 2014-01-01 51.650 2015-01-01 53.275 2016-01-01 55.275 2017-01-01 57.125