Year Percent 1991-01-01 0.76472100000000000 1992-01-01 0.71361500000000000 1993-01-01 0.83777400000000000 1994-01-01 0.82167600000000010 1995-01-01 0.83472600000000000 1996-01-01 0.70619600000000000 1997-01-01 0.60857400000000000 1998-01-01 0.55592800000000000 1999-01-01 0.58039200000000000 2000-01-01 0.49171600000000000 2001-01-01 0.61335000000000000 2002-01-01 0.54635700000000000 2003-01-01 0.51186300000000000 2004-01-01 0.43906000000000006 2005-01-01 0.46275900000000003 2006-01-01 0.43945100000000004 2007-01-01 0.43134799999999995 2008-01-01 0.52053500000000010 2009-01-01 0.61759300000000010 2010-01-01 0.28364600000000000 2011-01-01 0.25912900000000000 2012-01-01 0.25176000000000000 2013-01-01 0.22402800000000003 2014-01-01 0.20400800000000000 2015-01-01 0.19606200000000000