Year Percent 1986-01-01 0.40621199999999996 1987-01-01 0.40621199999999996 1988-01-01 0.40621199999999996 1989-01-01 0.40621199999999996 1990-01-01 0.40621199999999996 1991-01-01 0.40621199999999996 1992-01-01 0.40621199999999996 1993-01-01 0.40621199999999996 1994-01-01 0.40621199999999996 1995-01-01 0.40621199999999996 1996-01-01 0.40621199999999996 1997-01-01 0.40621199999999996 1998-01-01 0.40621199999999996 1999-01-01 0.40621199999999996 2000-01-01 16.78000000000000000 2001-01-01 15.66000000000000000 2002-01-01 14.45000000000000000 2003-01-01 15.63000000000000000 2004-01-01 16.02000000000000000 2005-01-01 17.83000000000000000 2006-01-01 17.53000000000000000 2007-01-01 14.68000000000000000 2008-01-01 8.02000000000000000 2009-01-01 9.82000000000000000 2010-01-01 7.91000000000000000 2011-01-01 6.15000000000000000 2012-01-01 7.30000000000000000 2013-01-01 7.28000000000000000 2014-01-01 6.70000000000000000 2015-01-01 6.65000000000000000 2016-01-01 5.99000000000000000