Year Percent 2001-01-01 20.075 2002-01-01 20.625 2003-01-01 20.850 2004-01-01 20.850 2005-01-01 19.475 2006-01-01 18.850 2007-01-01 18.600 2008-01-01 18.325 2009-01-01 18.625 2010-01-01 18.100 2011-01-01 17.575 2012-01-01 17.400 2013-01-01 16.650 2014-01-01 16.375 2015-01-01 16.475 2016-01-01 16.100 2017-01-01 15.700