Year Percent 2006-01-01 21.675 2007-01-01 21.775 2008-01-01 22.450 2009-01-01 23.200 2010-01-01 25.025 2011-01-01 26.650 2012-01-01 27.475 2013-01-01 28.300 2014-01-01 27.975 2015-01-01 28.825 2016-01-01 29.450 2017-01-01 30.350