Year Percent 2006-01-01 23.6000 2007-01-01 23.8000 2008-01-01 23.2000 2009-01-01 23.4000 2010-01-01 23.4320 2011-01-01 24.2252 2012-01-01 24.2625 2013-01-01 24.2831 2014-01-01 23.8098 2015-01-01 23.6119 2016-01-01 23.4903