Year Percent 2004-01-01 0.22 2005-01-01 0.61 2006-01-01 1.18 2007-01-01 1.79 2008-01-01 2.05 2009-01-01 3.59 2010-01-01 4.05 2011-01-01 3.87 2012-01-01 4.29 2013-01-01 4.61 2014-01-01 5.25 2015-01-01 5.83 2016-01-01 6.66