Year Percent 1996-01-01 78.3403 1997-01-01 82.1318 1998-01-01 81.9000 1999-01-01 85.9643 2000-01-01 84.4989 2001-01-01 87.0626 2002-01-01 55.0583 2003-01-01 70.5658 2004-01-01 79.4262 2005-01-01 85.2812 2006-01-01 84.8950 2007-01-01 89.7775 2008-01-01 89.4542 2009-01-01 78.8189 2010-01-01 77.2228 2011-01-01 80.7819 2012-01-01 82.9491 2013-01-01 85.1617 2014-01-01 87.2677 2015-01-01 85.5063 2016-01-01 84.9624