Year Percent 2005-01-01 40.700 2006-01-01 40.200 2007-01-01 40.100 2008-01-01 38.700 2009-01-01 38.400 2010-01-01 40.025 2011-01-01 39.450 2012-01-01 39.175 2013-01-01 38.850 2014-01-01 38.100 2015-01-01 37.700 2016-01-01 37.175 2017-01-01 37.400