Year Percent 2004-01-01 12.04 2005-01-01 13.02 2006-01-01 14.76 2007-01-01 15.09 2008-01-01 17.39 2009-01-01 15.98 2010-01-01 18.28 2011-01-01 19.07 2012-01-01 18.21 2013-01-01 16.63 2014-01-01 16.85