Year Percent 2005-01-01 34.5 2006-01-01 33.9 2007-01-01 33.3 2008-01-01 32.9 2009-01-01 32.6 2010-01-01 32.5 2011-01-01 32.3 2012-01-01 31.4 2013-01-01 30.7 2014-01-01 30.0 2015-01-01 29.5 2016-01-01 28.6