Year Percent 1998-01-01 57.1764 1999-01-01 46.4841 2000-01-01 55.7000 2001-01-01 57.3000 2002-01-01 57.4198 2003-01-01 55.6017 2004-01-01 53.9334 2005-01-01 55.0075 2006-01-01 57.4117 2007-01-01 55.6557 2008-01-01 48.9452 2009-01-01 51.8149 2010-01-01 54.3774 2011-01-01 54.9180 2012-01-01 53.5767 2013-01-01 53.9955 2014-01-01 54.7065 2015-01-01 54.7636