Year Percent 2008-01-01 0.36 2009-01-01 0.48 2010-01-01 0.57 2011-01-01 0.58 2012-01-01 0.64 2013-01-01 0.57 2014-01-01 0.69 2015-01-01 0.75 2016-01-01 0.87