Year Percent 1962-01-01 0.0937500000000000 1963-01-01 0.0906430000000000 1964-01-01 0.1170930000000000 1965-01-01 0.0690070000000000 1966-01-01 0.0690070000000000 1967-01-01 0.0690070000000000 1968-01-01 0.0690070000000000 1969-01-01 0.0690070000000000 1970-01-01 0.0690070000000000 1971-01-01 0.0690070000000000 1972-01-01 0.0019300000000000 1973-01-01 0.0026460000000000 1974-01-01 0.0055470000000000 1975-01-01 1.0678800000000000 1976-01-01 2.0762400000000003 1977-01-01 2.9601599999999997 1978-01-01 4.7621500000000000 1979-01-01 6.0375900000000000 1980-01-01 5.9131199999999990 1981-01-01 7.6864000000000000 1982-01-01 9.5872800000000000 1983-01-01 10.7016000000000000 1984-01-01 12.4817000000000000 1985-01-01 12.2715000000000000 1986-01-01 11.5373000000000000 1987-01-01 11.5171000000000000 1988-01-01 9.5232700000000000 1989-01-01 8.7709000000000000 1990-01-01 8.6641000000000000 1991-01-01 8.2479200000000000 1992-01-01 8.0714000000000000 1993-01-01 9.9632600000000000 1994-01-01 8.1970700000000000 1995-01-01 8.4220300000000000 1996-01-01 8.7417800000000000 1997-01-01 7.4277899999999990 1998-01-01 8.4012100000000000 1999-01-01 7.7687500000000000 2000-01-01 7.3684800000000000 2001-01-01 7.2844500000000000 2002-01-01 6.1404600000000000 2003-01-01 5.3135200000000000 2004-01-01 4.0885400000000000 2005-01-01 3.1224900000000000 2006-01-01 2.3404599999999998 2007-01-01 1.7409700000000001 2008-01-01 1.8995300000000000 2009-01-01 4.1264100000000000 2010-01-01 6.2076900000000000 2011-01-01 6.4531700000000000 2012-01-01 5.8754300000000010 2013-01-01 5.2863200000000000 2014-01-01 4.5293100000000000 2015-01-01 3.6593800000000000 2016-01-01 2.7813300000000000