Year Percent 1996-01-01 86.0237 1997-01-01 92.7082 1998-01-01 90.5766 1999-01-01 90.4283 2000-01-01 88.9884 2001-01-01 90.5818 2002-01-01 91.6633 2003-01-01 94.2508 2004-01-01 93.2911 2005-01-01 93.2701 2006-01-01 94.1628 2007-01-01 94.6249 2008-01-01 93.6996 2009-01-01 93.1844 2010-01-01 92.7741 2011-01-01 93.5609 2012-01-01 90.5617 2013-01-01 90.4150 2014-01-01 90.9388 2015-01-01 88.0943 2016-01-01 81.6228