Year Percent 1996-01-01 72.51140000000000 1997-01-01 80.99370000000000 1998-01-01 80.67399999999999 1999-01-01 74.84850000000000 2000-01-01 71.64310000000000 2001-01-01 81.85570000000000 2002-01-01 83.72820000000000 2003-01-01 81.39600000000000 2004-01-01 79.95680000000000 2005-01-01 81.88170000000000 2006-01-01 79.04470000000000 2007-01-01 76.74770000000000 2008-01-01 79.53440000000000 2009-01-01 77.74600000000001 2010-01-01 74.06910000000000 2011-01-01 72.03100000000000 2012-01-01 70.75180000000000 2013-01-01 72.52810000000000 2014-01-01 72.87730000000000 2015-01-01 69.71740000000000 2016-01-01 68.04920000000000