Year Percent 2008-01-01 1.31 2009-01-01 1.84 2010-01-01 2.16 2011-01-01 2.07 2012-01-01 2.41 2013-01-01 2.00 2014-01-01 1.69 2015-01-01 1.64 2016-01-01 1.60