Year Percent 1980-01-01 0.27117199999999997 1981-01-01 0.23462199999999997 1982-01-01 0.23462199999999997 1983-01-01 0.23462199999999997 1984-01-01 0.23462199999999997 1985-01-01 0.23462199999999997 1986-01-01 0.23462199999999997 1987-01-01 0.23462199999999997 1988-01-01 0.23462199999999997 1989-01-01 0.23462199999999997 1990-01-01 0.23462199999999997 1991-01-01 0.23462199999999997 1992-01-01 0.23462199999999997 1993-01-01 0.23462199999999997 1994-01-01 0.32065100000000000 1995-01-01 0.25161300000000003 1996-01-01 0.27754500000000000 1997-01-01 0.26622800000000000 1998-01-01 0.26622800000000000 1999-01-01 0.26622800000000000 2000-01-01 0.26622800000000000 2001-01-01 0.26622800000000000 2002-01-01 0.26622800000000000 2003-01-01 0.26622800000000000 2004-01-01 0.26622800000000000 2005-01-01 0.26622800000000000 2006-01-01 0.26622800000000000 2007-01-01 0.26622800000000000 2008-01-01 0.26622800000000000 2009-01-01 0.26622800000000000 2010-01-01 0.26622800000000000 2011-01-01 0.61681400000000010 2012-01-01 2.34795000000000000 2013-01-01 5.22860000000000000 2014-01-01 4.88446999999999900 2015-01-01 4.93687000000000000 2016-01-01 4.80134000000000000