Year Percent 2000-01-01 21.600000000000000 2001-01-01 18.200000000000000 2002-01-01 20.100000000000000 2003-01-01 22.300000000000000 2004-01-01 19.400000000000000 2005-01-01 19.300000000000000 2006-01-01 21.300000000000000 2007-01-01 20.200000000000000 2008-01-01 17.500000000000000 2009-01-01 17.800000000000000 2010-01-01 16.179000000000002 2011-01-01 16.076700000000000 2012-01-01 17.322600000000000 2013-01-01 19.816900000000000 2014-01-01 18.717800000000000 2015-01-01 21.276700000000000 2016-01-01 22.685900000000000