Year Percent 1990-01-01 0.12711000000000000 1991-01-01 0.13469500000000000 1992-01-01 0.15514500000000000 1993-01-01 0.16645800000000000 1994-01-01 0.22690500000000002 1995-01-01 0.23599200000000000 1996-01-01 0.17475700000000000 1997-01-01 0.22721999999999998 1998-01-01 0.22716200000000000 1999-01-01 0.21112800000000000 2000-01-01 0.18178400000000000 2001-01-01 0.21209099999999997 2002-01-01 0.22478800000000002 2003-01-01 0.21341900000000000 2004-01-01 0.21432300000000000 2005-01-01 0.21674100000000000 2006-01-01 0.21672399999999997 2007-01-01 0.22193500000000000 2008-01-01 0.21505300000000002 2009-01-01 0.24930200000000000 2010-01-01 0.22855900000000000 2011-01-01 0.23610900000000000 2012-01-01 0.24118600000000000 2013-01-01 0.21195999999999998 2014-01-01 0.18656600000000000 2015-01-01 0.17866100000000000