Year Percent 2004-01-01 10.76 2005-01-01 10.76 2006-01-01 14.31 2007-01-01 14.75 2008-01-01 15.52 2009-01-01 4.59 2010-01-01 17.44 2011-01-01 17.66 2012-01-01 17.93 2013-01-01 18.35 2014-01-01 19.37 2015-01-01 19.98