Year Percent 2005-01-01 62.3 2006-01-01 63.2 2007-01-01 63.9 2008-01-01 64.3 2009-01-01 63.2 2010-01-01 63.0 2011-01-01 63.5 2012-01-01 64.4 2013-01-01 65.1 2014-01-01 66.1 2015-01-01 66.8 2016-01-01 67.8