Year Percent 2006-01-01 36.275 2007-01-01 36.500 2008-01-01 37.150 2009-01-01 37.450 2010-01-01 37.375 2011-01-01 38.475 2012-01-01 37.350 2013-01-01 38.800 2014-01-01 40.775 2015-01-01 41.775 2016-01-01 42.350 2017-01-01 43.200