Year Percent 1998-01-01 60.450 1999-01-01 59.700 2000-01-01 59.700 2001-01-01 60.525 2002-01-01 59.875 2003-01-01 59.200 2004-01-01 57.975 2005-01-01 57.850 2006-01-01 57.575 2007-01-01 57.650 2008-01-01 57.575 2009-01-01 56.500 2010-01-01 55.925 2011-01-01 56.225 2012-01-01 56.025 2013-01-01 56.250 2014-01-01 55.925 2015-01-01 55.250 2016-01-01 55.000 2017-01-01 55.250