Year Percent 2003-01-01 18.675 2004-01-01 19.800 2005-01-01 18.650 2006-01-01 17.525 2007-01-01 17.325 2008-01-01 18.100 2009-01-01 19.650 2010-01-01 19.625 2011-01-01 20.225 2012-01-01 20.125 2013-01-01 19.350 2014-01-01 17.850 2015-01-01 17.000 2016-01-01 16.200 2017-01-01 17.100