Year Percent 2005-01-01 80.0 2006-01-01 80.2 2007-01-01 80.2 2008-01-01 80.2 2009-01-01 79.7 2010-01-01 79.4 2011-01-01 79.3 2012-01-01 79.4 2013-01-01 79.4 2014-01-01 79.5 2015-01-01 79.6 2016-01-01 79.9