Year Percent 2006-01-01 24 2007-01-01 24.0 2008-01-01 24.0 2009-01-01 24.0 2010-01-01 24.0 2011-01-01 24.0 2012-01-01 24.0 2013-01-01 24.0 2014-01-01 21.7