Year Percent 1974-01-01 0.41822500000000000 1975-01-01 0.74261000000000000 1976-01-01 0.59087800000000000 1977-01-01 0.49923599999999996 1978-01-01 0.47827700000000006 1979-01-01 0.41008400000000000 1980-01-01 0.44981099999999996 1981-01-01 0.42295299999999997 1982-01-01 0.35354500000000000 1983-01-01 0.37927500000000000 1984-01-01 0.51041500000000000 1985-01-01 0.62360900000000000 1986-01-01 0.83848899999999990 1987-01-01 0.72239600000000000 1988-01-01 0.68845700000000000 1989-01-01 0.60707600000000010 1990-01-01 0.55996400000000000 1991-01-01 0.55927700000000000 1992-01-01 0.77493300000000000 1993-01-01 0.98785800000000000 1994-01-01 0.44164100000000000 1995-01-01 0.40967200000000004 1996-01-01 0.22628700000000000 1997-01-01 0.28907700000000000 1998-01-01 0.90444200000000000 1999-01-01 1.31941000000000000 2000-01-01 0.80209300000000010 2001-01-01 1.12952000000000000 2002-01-01 0.87381000000000010 2003-01-01 0.93291299999999990 2004-01-01 1.95592000000000000 2005-01-01 1.94911000000000000 2006-01-01 2.14187000000000000 2007-01-01 1.84907000000000000 2008-01-01 1.73459000000000000 2009-01-01 1.88464000000000000 2010-01-01 2.34835000000000000 2011-01-01 2.58902000000000000 2012-01-01 2.18724000000000000 2013-01-01 1.90234000000000010 2014-01-01 2.65852000000000000 2015-01-01 2.36532000000000000 2016-01-01 2.31704000000000000 2017-01-01 2.43554000000000000