Year Percent 1996-01-01 93.00010000000000 1997-01-01 87.06400000000000 1998-01-01 85.82680000000000 1999-01-01 87.00640000000000 2000-01-01 85.09260000000000 2001-01-01 87.86100000000000 2002-01-01 85.56810000000000 2003-01-01 88.93530000000000 2004-01-01 85.30180000000000 2005-01-01 92.89780000000000 2006-01-01 81.18480000000000 2007-01-01 70.74190000000000 2008-01-01 62.94850000000000 2009-01-01 68.68340000000000 2010-01-01 71.35910000000000 2011-01-01 72.74450000000000 2012-01-01 84.34700000000001 2013-01-01 83.75460000000000 2014-01-01 85.63360000000000 2015-01-01 80.47410000000000 2016-01-01 77.87960000000000