Year Percent 1998-01-01 17.7000 1999-01-01 17.5000 2000-01-01 16.2000 2001-01-01 15.6000 2002-01-01 16.9000 2003-01-01 17.4000 2004-01-01 18.4000 2005-01-01 17.7000 2006-01-01 17.5000 2007-01-01 15.7000 2008-01-01 14.9000 2009-01-01 15.5000 2010-01-01 16.6882 2011-01-01 17.1210 2012-01-01 17.8218 2013-01-01 17.0169 2014-01-01 16.0804 2015-01-01 15.2847 2016-01-01 14.4643