Year Percent 2000-01-01 50.125 2001-01-01 48.750 2002-01-01 47.025 2003-01-01 46.650 2004-01-01 47.100 2005-01-01 48.200 2006-01-01 49.675 2007-01-01 52.025 2008-01-01 54.175 2009-01-01 54.375 2010-01-01 53.950 2011-01-01 54.225 2012-01-01 54.400 2013-01-01 54.425 2014-01-01 55.625 2015-01-01 56.500 2016-01-01 57.550 2017-01-01 58.575