Year Percent 2007-01-01 0.01 2008-01-01 0.01 2009-01-01 0.02 2010-01-01 0.02 2011-01-01 0.04 2012-01-01 0.04 2013-01-01 0.54 2014-01-01 0.61 2015-01-01 0.64 2016-01-01 0.68