Year Percent 2000-01-01 0.30074400000000000 2001-01-01 0.27132700000000000 2002-01-01 0.22101700000000002 2003-01-01 0.19797200000000000 2004-01-01 0.19564700000000002 2005-01-01 0.21308300000000000 2006-01-01 0.20678600000000003 2007-01-01 0.24570400000000000 2008-01-01 0.24901199999999998 2009-01-01 0.25468300000000000 2010-01-01 0.28870100000000004 2011-01-01 0.31811700000000000 2012-01-01 0.31376500000000000 2013-01-01 0.17071800000000000 2014-01-01 0.20802800000000002 2015-01-01 0.25772900000000000