Year Percent 1996-01-01 58.442900000000000 1997-01-01 68.097700000000000 1998-01-01 68.458600000000000 1999-01-01 58.186000000000010 2000-01-01 57.444400000000000 2001-01-01 66.384800000000000 2002-01-01 66.466100000000000 2003-01-01 63.596000000000004 2004-01-01 62.425700000000000 2005-01-01 62.482400000000000 2006-01-01 59.424000000000000 2007-01-01 56.265300000000000 2008-01-01 58.807500000000000 2009-01-01 58.056900000000000 2010-01-01 55.103600000000000 2011-01-01 52.740000000000000 2012-01-01 50.942900000000000 2013-01-01 52.248500000000000 2014-01-01 51.613900000000000 2015-01-01 54.399400000000000 2016-01-01 52.570600000000000