Year Percent 2002-01-01 0.46 2003-01-01 0.44 2004-01-01 0.45 2005-01-01 0.44 2006-01-01 0.43 2007-01-01 0.47 2008-01-01 1.05 2009-01-01 1.15 2010-01-01 1.22 2011-01-01 1.32 2012-01-01 1.54 2013-01-01 1.73 2014-01-01 1.81 2015-01-01 2.01