Year Percent 2000-01-01 56.925 2001-01-01 57.575 2002-01-01 57.375 2003-01-01 57.350 2004-01-01 58.025 2005-01-01 59.275 2006-01-01 60.375 2007-01-01 63.325 2008-01-01 61.475 2009-01-01 56.025 2010-01-01 53.500 2011-01-01 52.450 2012-01-01 52.125 2013-01-01 53.450 2014-01-01 54.425 2015-01-01 55.700 2016-01-01 57.000 2017-01-01 57.825