Year Percent 2005-01-01 17.850 2006-01-01 16.550 2007-01-01 14.975 2008-01-01 15.525 2009-01-01 20.025 2010-01-01 20.950 2011-01-01 21.225 2012-01-01 23.450 2013-01-01 24.225 2014-01-01 23.725 2015-01-01 22.350 2016-01-01 20.900 2017-01-01 18.800