Year Percent 1996-01-01 74.3369 1997-01-01 64.8793 1998-01-01 56.1809 1999-01-01 62.4723 2000-01-01 63.8197 2001-01-01 63.0926 2002-01-01 67.6391 2003-01-01 73.8385 2004-01-01 71.7866 2005-01-01 71.1758 2006-01-01 69.2465 2007-01-01 71.9285 2008-01-01 69.9896 2009-01-01 77.0572 2010-01-01 75.5349 2011-01-01 79.1188 2012-01-01 79.3075 2013-01-01 67.9680 2014-01-01 68.7916 2015-01-01 67.3893 2016-01-01 66.1737