Year Percent 2003-01-01 14.39 2004-01-01 16.65 2005-01-01 19.49 2006-01-01 16.25 2007-01-01 16.39 2008-01-01 12.67 2009-01-01 16.33 2010-01-01 17.93 2011-01-01 15.21 2012-01-01 17.15 2013-01-01 21.85 2014-01-01 23.70 2015-01-01 19.71 2016-01-01 17.54