Year Percent 1998-01-01 51.9663 1999-01-01 58.3643 2000-01-01 55.7000 2001-01-01 45.8000 2002-01-01 46.5052 2003-01-01 52.6689 2004-01-01 55.7379 2005-01-01 52.3244 2006-01-01 50.6870 2007-01-01 54.6252 2008-01-01 42.2175 2009-01-01 47.9548 2010-01-01 51.8956 2011-01-01 44.4342 2012-01-01 46.8947 2013-01-01 51.6722 2014-01-01 49.3247 2015-01-01 49.1193 2016-01-01 48.3591