Year Percent 2006-01-01 20.975 2007-01-01 21.000 2008-01-01 21.625 2009-01-01 22.275 2010-01-01 24.025 2011-01-01 25.575 2012-01-01 26.300 2013-01-01 27.100 2014-01-01 26.675 2015-01-01 27.450 2016-01-01 28.000 2017-01-01 28.875