Year Percent 1997-01-01 0.21210700000000002 1998-01-01 0.20572800000000002 1999-01-01 0.40262500000000000 2000-01-01 0.18783600000000000 2001-01-01 0.18062200000000000 2002-01-01 0.17604500000000000 2003-01-01 0.17612000000000000 2004-01-01 0.20756200000000000 2005-01-01 0.23176700000000000 2006-01-01 0.24768400000000002 2007-01-01 0.26177300000000000 2008-01-01 0.34445500000000000 2009-01-01 0.28166700000000000 2010-01-01 0.30852700000000000 2011-01-01 0.33086500000000000 2012-01-01 0.29020200000000000 2013-01-01 0.28679099999999996 2014-01-01 0.29556500000000000 2015-01-01 0.41645900000000000 2016-01-01 0.48744200000000000